The (marine) Fish Tank

Whether a goldfish won at a fair, a trip to the aquarium, or the tank which has newly emerged in the biology corridor (as some of you may have noticed), the explosion in the ornamental fish trade is evident, with the global marine fish industry valued at 4.89 billion USD (2020) [1], and projected to grow to a size of 8.4 billion by 2027 [2]. Over 20 million fish are harvested each year for this trade, 65% of which is sourced from the Philippines, and the USA importing 50-60% of the global trade [3].

This hobby is propelled by the newfound interest of starting a personal reef aquarium, linking to either general interest in the hobby, or the human desire to seek beauty, unparalleled by the stunning organisms witnessed within the marine ecosystem. This means for huge imports of marine livestock every year, composed of fish, corals, and invertebrates, as well as “live” rock (discussed paragraph 1). Within this article, I will discuss the science between synthesising the very delicate ecosystem of a coral reef, the processes involved, as well as delving into the ethical issues which the hobby surfaces, such as the environmental threat and the moral implications of importing organisms which are almost guaranteed to die under captivity.

Section 1 – Why do my fish keep dying?

For every new fish keeper, there is always a looming possibility that one day you will look over to your fish tank and see something floating on the water line. There are a variety of reasons why our tank inhabitants may succumb, whether it may simply be from old age, disease, or starvation. However, the most prominent cause of fish death within our enclosed ecosystems is poor water quality. When a fish dies within a very new tank, it is almost always because the tank hasn’t been “cycled”. The basis of a tank, whether freshwater or marine, relies on a process called the nitrogen cycle. This process uses nitrifying bacteria (in this context usually Nitrobactersp or Nitrosomonassp.) in order to convert some of the more harmful toxins found in fish waste (ammonia) into less harmful substances (nitrites, nitrates). Therefore, it is mandatory to have a live colony of bacteria in aquaria before introducing organisms to ensure that their waste products aren’t of any threat. This can be done a variety of ways: a new marine tank can either be filled with “live” sand and/or “live” rock. These usually either come from the ocean or from an already established tank, and are “live” in the sense of the already established populations of nitrifying bacteria they contain. They can therefore introduce a population into the tank, established after cycling the tank for a few weeks, a process that includes adding organic matter into the water, to introduce ammonia into the tank, helping the bacteria to establish for a few weeks, before the introduction of any fish. Popular alternatives that have since recently arisen include bottled strains of nitrifying bacteria that the fish keeper can simply supplement into the tank, to introduce and maintain a healthy population.

Where does ammonia come from?

Ammonia (or NH3) is a naturally occurring substance resulting from the decomposition of organic matter In animals, this is due to reactions such as deamination [4] (hydrolysis of an amino acid which causes the release of an amine group) Within humans, we convert this harmful substance into urea in our liver, which is comparatively safer, and remove it through our urine, totalling 80% of the nitrogen we egest [5]. However, this process of conversion is metabolically costly, which means that it is only largely done by large vertebrates such as mammals. Instead of this, the urine of fish contain a smaller amount of urea, directly removing ammonia instead. Outside of organisms, decomposing organic nitrogenous waste goes through a process called ammonification, or mineralisation, whereby bacteria and other decomposers convert the organic nitrogen into ammonia (NH3) or ammonium (NH4+) They depolymerise the components of the organic matter such as proteins into amino acids, then hydrolysed into ammonium.

Deamination of cyocystine into uracil, producing ammonia as a byproduct

Why is ammonia harmful to fish?

There are two forms of ammonia: ionised (ammonium) and unionised (ammonia) Whilst ammonium is harmless due to its inability to pass through a fish’s gills, unionised ammonia is highly toxic to most vertebrates, including fish, which make keeping them in an enclosed body of water difficult, as if unsupervised, this substance can build up and swiftly cause premature death. The problem is also exacerbated at higher pH due to both the fact that there are less hydrogen ions available therefore a lower amount of ammonium and a larger amount of ammonia [6]. This also causes a shallower diffusion gradient, meaning that the rate of ammonia expelled from the organism is lower, without active transport, causing potential build ups. Firstly, ammonia damages the gills of fish due to causing immense oxidative stress, and creating “burns” on the fish. Once inside the fish, due to the difference in the pH of the blood, the equilibrium constant switches, meaning that most ammonia, once kit has entered the fish, will exist instead in the form of ionised ammonium. This can then cause many issues to the fish’s metabolic processes. One of them include involuntarily increasing the amount of glycolysis reactions which occur (producing

ATP without the need for oxygen). This happens as it activates the enzyme, one of the essential enzymes needed in the process. Another problem it induces relates to aerobic respiration within the mitochondria: it interferes with the tricarboxylic acid cycle. It also interferes with the transport of ions, primarily being substituted for K+. This affects the nervous system [7].

Nitrogen cycle

The dissolved ammonia and ammonium is removed through the nitrogen cycle, ending up with a product of nitrate. Firstly, the ammonia is converted by Nitrosomonassp. Bacteria [8]. These bacteria are distributed all throughout almost every habitat, both terrestrial and aquatic. However, the more marine adapted species of Nitrosomonas bacteria include N.marinaas well as N. aestuariiand therefore would be the varieties commonly found in saltwater aquaria. However, they all have practically the same process, which is the oxidation of ammonia in order to convert it into nitrite. Unfortunately, there is not sufficient literature to be sure of what happens at each step, but there is a rough outline as to the reactions which occur. Within the bacteria, the ammonia or ammonium is first converted into hydroxylamine (NH2OH) by the addition of oxygen and an electron pair, thought to be donated by the compound ubiquinol. This reaction also requires the enzyme AMO (ammonia mono-oxygenase). This compound is then reduced to form NO2- using the enzyme hydroxylamine dehydrogenase [8]. The second stage of nitrification is the conversion of nitrite into nitrate. This is done by the bacteria in the genuses nitrobacterand nitrospira Using the NO2-, they oxidise the nitrite into nitrate using the enzyme nitrite oxidoreductase, producing two hydrogen ions, two electrons, and a nitrate (NO3-) ion The H+ ions and electrons can then be combined with oxygen in order to form two molecules of water. Doing this reaction, the H+ ions can produce 47kJ of energy per molecule of nitrite for the bacteria [9].

Theinternalprocesseswithinthenitriteoxidisernitrospira[10]

Why do copper and chlorine harm inverts/fish?

It is no surprise that the presence of any heavy metals has a profound effect on fish. After all, these elements also have the ability to induce severe harm in humans, as we have seen in mass outbreak of poisonings such as the “itai-iati”“disease” in Japan, literally translating to “it hurts-it hurts”, this outbreak was primarily caused by cadmium poisoning as a result of contaminated waste from mining entering into water systems, and being uptaken by fish or absorbed by the rice crop. Within the saltwater aquarium, there is one metal which should be avoided at all costs because, whilst in small amounts it can be tolerated by fish, it can wreak havoc on invertebrates, including corals, and bringing them a swift death. This metal is copper. Thus it is often used in fish-only freshwater tanks as a pest killer for planaria/snail/flatworm/algae/parasites, but if used wrongly, can kill shrimp and ornamental snails. In UK tap water, the maximum amount of copper contained is 1.3mg/l, aligning with EPA recommendations [11]. However, the maximum copper tolerance in corals ranges from around 0.01-0.1mg/l. Thus, most hobbyists, in fear of heavy metals as well as additional phosphates, nitrates and chlorine, opt to instead use RO (reverse osmosis) water, meaning that everything has been removed through very intricate filtration except for the pure water. Within water, copper usually exists as Cu2+ ions [12]. Similarly to ammonia, pH affects the amount that is active.

Bicarbonate ions as well as forms of carbonate will all bond to the copper ion The acidity of the water influences the amount of these binders, therefore the amount of copper accessible. As well as this, a lower pH may cause previously bound copper to release.

There is not much literature on the effects of the copper ions on these organisms. However, it may link to the fact that most aquatic invertebrates, must have some degree of copper within them in order to synthesise the blood pigment hemocyanin, which carries oxygen in the place of haemoglobin which is contained in our red blood cells, and and carries a Fe+ ion. It is though that copper, in Gastropoda including mollusks and bivalves, may bond to the hydrophilic bilayers of their epithelial cells, which then changes their properties and interferes with their function, being the major cause of death. Copper may also interfere with the function of the enzyme peroxidase and protein ferritin, causing them to produce hydroperoxides and malondialdehyde, which severely damage the function of cell and membranes. In crustaceans such as crabs, copper disturbs the concentration gradient in the gills, which decreases the amount of oxygen reaching the blood [13].

Another reason fish often succumb to the care of the new hobbyist is due to a different element: chlorine, as well as its forms such as chloramines (combination of chlorine and ammonia) This occurs if the hobbyist is not using RO or a tap water conditioner. In the UK, tap water often contains less than 1mg/l of this substance, and the maximum amount is 5mg/l [14]. It is added to kill microbes including pathogens, making the drinking water more safe. However, chlorine can be lethal to fish in concentrations as little as 0.1mg/l, meaning that tap water often contains enough water to kill most of the more delicate species, and maybe even those more hardy, depending to the concentration of chlorine. Thus, it is imperative to introduce some form of chlorine removal before the water is added to the tank. The most popular option is currently the use of a tap water conditioner.This removes not only chlorine, but also heavy metals from the water. Another method which is less costly would simply to be leave the water for a period of time, or boil it. This works as chlorine is a gas at room temperature, with a boiling point of -34.04 degrees Celsius, meaning that left a period of time, it will evaporate and leave the water. Free chlorine is more toxic to organisms than chloramine [15], which makes chlorine poisoning more abundant at lower a pH due to the larger availability of free chlorine. This links back to the equilibrium between ammonia, hydrogen ions and ammonium. As the pH is lower, there will be a larger availability of hydrogen ions, meaning there will be more ammonium. Therefore, there will be less ammonia, meaning less chloramines a formed, resulting in a larger number of the more lethal free chlorine.

Chlorine, being a very reactive element, can cause severe burns due to its high corrosivity when it makes contact with the fish. This is primarily at the gills, however, will continue inside the fish should chlorine enter through the bloodstream. This is the reason why chlorine is generally more dangerous than chloramines. However, chloramines can also become lethal if a cheaper tap water conditioner is used. This is because, whilst they treat the chlorine, and converting it into harmless chlorides, this frees the ammonia which is arguably more lethal to the fish. One of the main reasons for which chlorine is such a rapid killer, however, relates to the fact that it oxidises the haemoglobin in the blood into methemoglobin [16], meaning that no oxygen can be carried and the fish suffocates. This means that larger fish fare worse, as they have a decreased volume : gill surface area ratio, meaning that they need to be more efficient with absorbing oxygen into their bloodstream.

Animals or plants? – Well, technically both

Apart from the occasional hydroid or the elusive freshwater jellyfish (Craspedacusta sowerbii), one of the major separations of freshwater and saltwater is the distinct lack of notable cnidarians within freshwater. Cnidarians are a phylum of invertebrates which is partly defined by the presence of nematocysts (cnidocyte), or stinging cells. Cnidarians are the foundation of coral reefs, quite literally, as this diverse phylum encompasses corals. Not only this, but other famous inhabitants of this phylum include anemones and jellyfish, but also hydrozoa such as siphonophores and cnetophores such as sea combs and sea gooseberries. This phylum comprises of over 11,000 species and some of the most interesting organisms in the world. For the purpose of this article, I am going to narrow this down to the behaviours and biology of anemones and corals, as they are most often collected and now propagated, maricultured, and aquacultured for the purpose of our hobby. Jellyfish are still verging on very difficult to maintain, requiring special conditions which cannot be met with a standard reef aquarium, such as a rounded tank with continuous circular flow as well as the addition of small live zooplankton, with baby brine shrimp often used in the hobby. However, exceptions do exist such as the upside-down jellyfish (Cassiopea sp.) Cnetophores verge on impossible, with one of the only places capable to meeting their needs (Monterey Bay Aquarium) describing them as “badly organised water”.

What makes coral interesting? Not only are they incredibly diverse, have stunning beauty, and support 25% of marine life, but they also are mostly comprised of two different organisms working together and forming a symbiotic relationship. This is between the coral and the anemone itself, and the zooxanthellae which inhabit their tissues. Corals can come in many different varieties, most of them considered to be reef-building. They consist of often many polyps which multiply and form large colonies. These polyps often have their own “mouths”, but the colony shares a singular gastrovascular system, which means that nutrition and circulation is distributed throughout the colony [17]. There are also types of corals (e.g. scolymia, fungia, heliofungia, cyarina, and acanthophyllia) which only consist of a singular solitary polyp. Reef-building corals also are usually comprised of a calcium carbonate skeleton, but some corals, called soft corals, do not have a skeleton. Members include the subclass Octocorallia (gorgonians, dendronephthya, wire corals, leather corals, sea pens), as well as the orders Corallimorpharia(mushroom corals) and Zoantharia (zoanthids). Corals are then divided once again: photosynthetic and nonphotosynthetic. Photosynthetic contain the symbiotic zooxanthellae whilst nonphotosynthetic species do not. This means that non-photosynthetic corals rely on capturing zooplankton, phytoplankton and various organic matter for their nutrition.

On the other hand, photosynthetic corals derive their energy from their zooxanthellae, an umbrella term for varieties of photosynthetic algae which inhabit another living organism in a symbiotic relationship. The varieties found within corals vary from 812 micrometers in size and specifically inhabit the gastrodermal cells of the coral – a layer of cells just beneath the epidermis of the organism, including the structure chloroplasts which are the site of the photosynthesis [17]. Both organisms in this process benefit. Firstly, the coral receives some of the products of photosynthesis from the algae, in the form of reduced carbon, aiding respiration. Also, the coral receives some protection from potentially toxic compounds which can be absorbed by the algae. On the other hand, the algae not only receives protection, but receives carbon dioxide and nutrients from the coral, aiding in photosynthesis and growth. However, this relationship also introduces new factors and risks, such as limitations for where the coral can survive, as well as the possibility for algal overgrowth which in return puts the algae at risk of expulsion from the coral host. This is one of the major reasons why bleaching occurs, in which a coral expels its symbiotic zooxanthellae due to environmental factors such as undesirable temperatures and amount of light, factors affecting the growth rate of the algae. This leaves the coral unable to source enough food, even in the ocean, let alone our aquaria, and causes it to starve. Due to a coral’s pigmentation being a result of the inhabiting zooxanthellae, bleaching causes the colony to lose pigment, resulting in a bone white colour.

It is often wondered where the zooxanthellae within the coral comes from. The answer to this question is determined by the species of coral. Some corals, such as mushroom corals, “candy-cane” corals (Caulastreasp.), and elegance corals (Cataphylliajardinei) reproduce asexually. This means the lack of two parent organisms. This can happen in a number of ways. For example, mushroom corals can employ pedal laceration, whereby they move and pieces of their “foot” detach and form separate colonies, candy-cane corals use longitudinal fission, whereby the polyps form two mouths which then pull away from each other, forming two heads, and elegance corals go through budding, where pieces of the mother colony drop off and form new colonies. Within the hobby, in aquaculture, the most popular method of producing new colonies is called “fragging”. In this process, a section of a coral colony, normally consisting of one or more heads, is separating through the use of bone cutters or a saw. This piece can then form a new colony. In some single-polyp corals, or some anemones, hobbyists can split the coral vertically down, often using a razor blade for anemones, making sure to pass through the mouth. These two halves, if not succumbed to infection, can form two new polyps. However, in some species such as scolymia, the healing and reformation of the two halves into their valuable circular shape an take up to 10 years, making it not a cost effective process. Through asexual reproduction, zooxanthellae is passed directly from the mother colony to the offspring.

However, in the wild, many corals rely on sexual reproduction as the most effective way of producing offspring. The majority of corals rely on external fertilisation whereby, in mass spawning events, they synchronise the release of their eggs and sperm with the lunar cycle as to maximise the chance of offspring production. These organisms are also hermaphroditic, meaning that they contain both gametes. Some corals employ buoyant packages of egg and sperm which float to the water’s surface and then break apart. Some corals, called brooders, fertilise internally and then release the developed planulae [18]. On one hand, external fertilisation offers wider genetic variation, greater distance of dispersion, and require less energy. On the other hand, internal fertilisation produces offspring with a higher chance of survival due to being developed enough to be able to settle and form a polyp just after being released. In sexual reproduction, zooxanthellae can either be acquired directly (vertically) or indirectly (horizontally). Direct transfer means that the mother colony includes zooxanthellae already within the egg. The majority of corals acquire their zooxanthellae indirectly, that is, the eggs do not contain zooxanthellae, but instead, they must acquire it through phagocytosis, in which the zooxanthellae enters through the gastrovascular cavity (mouth). This occurs when the larvae are still in their motile stage. Studies show that zooxanthellae show positive chemotaxis (movement according to concentration) towards coral which have a lower amount of or no zooxanthellae. There is also a possibility of a coral obtaining zooxanthellae through the consumption of fecal matter from organisms which consume those with zooxanthellae: broadly coral, anemone and jellyfish eaters [19].

As previously mentioned, the presence of zooxanthellae is not only limited to corals. There are many other species of organisms it is known to co-inhabit with. The most famous example of this would be the anemone. Once again, not all anemones contain this algae. Similar to corals, the anemone either obtains this from asexual reproduction or direct/ indirect acquisition [20]. Other examples of organisms that pair with zooxanthellae include Tridacna clams, jellyfish such as Cassiopeasp., and sea slugs such as the lettuce sea slug (Elysiacrispata) and the sea sheep (Costasiella kuroshimae). The interesting fact about these slugs is that they acquire the chloroplasts for photosynthesis through their diet of algae This process is called kleptoplasty, where the alga consumed is partially digested and the chloroplasts are then phagocytosed by the digestive cells and then used within the host organism. We see this kind of relationship in other types of sea slugs (nudibranchs) which steal the nematocysts from the hydroids they consume, and then recycle them for their own defence purposes.

Other forms of mutualism, commensalism and parasitism within the marine aquarium

Despite common misconceptions, symbiotic relationship doesn’t mean that both parties benefit. It is an umbrella term encompassing mutualism (both organisms benefit), commensalism (one organism benefits and the other is unaffected), and parisitism (one organism benefits and the other suffers). There is one iconic symbiotic relationship in the marine hobby, extremely popularised by the film ‘Finding Nemo”, which has led to many children and adults to enter the hobby. That is, the pairing between clownfish and and anemones. In particular, the iconic orange and black striped clownfish look comes from the ocellaris clownfish. This particular species is capable of pairing with the magnificent sea anemone (Heteractismagnifica), giant carpet anemone (Stichodactylagigantea) and (within the hobby) the bubble-tip anemone (Entacmaeaquadricolor). However, if these anemones are not available, clownfish are known to take host within similar corals, such as those in the genus euphilliidae This relationship is symbiotic as both members benefit: the clownfish is provided shelter and safety from predators by the anemone’s powerful sting. The clownfish also uses the anemone in order to obtain food: they do this by luring larger fish into the anemone, and then letting it get killed by nematocysts, and feasting on the remains. The anemone is provided both the clownfish’s waste products and its protection from predators such as butterflyfish.

Why are clownfish not stung by anemones?

The clownfish themselves avoid being stung by their host anemone. There are currently many opposing hypotheses as to why this occurs. However, there is some general consensus that a crucial factor would lie within the thick mucus coating which envelops the clownfish, as the flesh of the clownfish cannot withstand the sting of an anemone The most widely believed theory states that the anemone is a passive partner, rather than reacting differently in the presence of a clownfish. It instead argues that the clownfish’s thick mucus coating is produced by the clownfish when it comes into contact with the anemone, and does not trigger a different chemical response from the nematocysts, but instead that the coating itself is enough to prevent the firing nematocysts from causing harm to the clownfish [21]. A study showed that, when clownfish were removed from their anemone and returned 1-3 days later, they would be stung for a period of acclimation to the anemone. Another theory suggests that the anemone produces quantities of protective substances. Whilst non-symbiotic fish would rarely come into contact with the anemone, and thus would be stung, symbiotic fish would repeatedly rub on the anemone to acclimatise, and therefore acquire some of the defensive substances which incorporates into their mucus [22]. This could either be the anemone recognising the fish as symbiotic, or as a part of itself, due to the common antigens. A test showed that clownfish which came into contact with anemones contained antigens within their mucus which were anemone-exclusive

How do clownfish know to find an anemone?

Clownfish seem to have an innate sense of guidance towards finding an anemone, as an evolutionary factor where the clownfish finds the anemone by chemical signalling However, a test showed there is also some form of imprinting which plays a factor in the ability of a clownfish to recognise an anemone. Eggs from Amphiprionocellaris were raised in two environments: one in the presence of a host anemone, and one without. When moved into an environment with an anemone and hatched, the larvae which had been reared in the presence of an anemone immediately found the anemone within 5 minutes, whilst the ones which had not did not find it within a 48 hour time period. However, a study also showed that the innate guidance appeared within the fish once reaching the stage of development where the fish would look for settlement. In a different test, which involved two compartments of water connected by a Perspex flume. One of the bodies of water contained “anemone seawater” (water that had been in a tank for 12 hours with a host anemone. The clownfish of different development stages were added and then measured as to which body of water they would prefer to stay in. The results showed that the majority of the clownfish, at every stage of development would prefer to stay within the “anemone water”. I believe that imprinting or environmental factors must play a large role in the locating of a host. In the school marine tank, within the 3 months, our clownfish have failed to locate the host anemone Entacmaeaquadricolor Many other hobbyists experience the same problem. Sometimes, it is simply the problem that they have not located the anemone, and other times they simply do not wish to host within it. This probably links to the factor of imprinting. This is because most clownfish are now tank bred, being one of the most successfully aquacultured marine fish. This could mean for a lack of initial imprinting of an anemone. The fact that wild caught clownfish have a better tendency to host an anemone in captivity reflects this. This also may relate to environmental factors. Within aquaria, there is little to risk of predation to the clownfish, which nullifies their need of an anemone. Finally, it may relate to the fact that Entacmaeaquadricoloris not naturally usually a host for Amphiprionocellaris.

Other notable mutualism with marine aquaria

There are many other very interesting mutualistic relationships found within the ocean, a handful of which are suitable for our aquarium conditions. It is not only clownfish which host anemones. For example, Pederson’s cleaner shrimp (Ancylomenespedersoni) forms a mutualistic relationship with anemones of the genus condylactis, sexy shrimp (Thoramboinensis) with the carpet anemone Stichodactyla sp., peacock-tail anemone shrimp (Periclimenesbrevicarpalis) with various types of anemone, the porcelain anemone crab (Neopetrolisthesmaculatus) with various species of anemone, and many more. One of the unusual partnerships is the “walking dendro” coral (Heteropsammiacochlea). This species acquires its name due to its unique ability to move around on the sandbed. However, it is not the coral itself which is instigating this movement. Instead, it is the work of its partner, a peanut worm from the family aspidosiphonidae. These worms inhabit a small hole within the hole of the coral, and drag the coral around for movement. The worm benefits as it receives protection and the coral benefits as the movement prevents it from being buried within the sandy areas they inhabit. Another interesting mutualistic relationship is that between the pistol/snapping shrimp of the genus Alpheusand several species of gobies in the genera Amblyeleotrisand Cryptocentrus. In this situation, the shrimp digs within the sand a tunnel which it and the goby co-inhabit. Due to the shrimp’s poor eyesight, the goby keeps watch for potential threat and alerts the shrimp, allowing them to retreat into the burrow. Thus both members benefit and their safety is maintained. It appears that this relationship is also maintained and born through a series of innate chemical cues. Finally, there is the anemone hermit crab (Dardanus pedunculatus) As the name suggests, the anemone hermit crab “wears” several anemones on its shell from the genera Adamsiaand Stylobates The crab is offered from protection from predators such as cephalopods, and the anemone is offered transport which helps to locate food, and a degree of protection from the crab.

Collecting of wild fish and organisms

With our marine ecosystem already at huge strain due to the variety of human-caused attacks on it, such as global warming, ocean acidification, plastic pollution, overfishing, eutrophication and oil spills causing issues such as mass bleaching, build ups of microplastics throughout the food chain, the endangerment of many organisms, especially those of higher trophic level, and an imbalance in the food chain, would it be ethical to additionally pile on the strain of the hobby, extracting between 18-30 million fish each year, from already vulnerable ecosystems such as coral reefs, in order to fuel our hobbies? To evaluate this, we must break down the problem into segments, the severity of their effects and observe it through different moral standards.

According to Kantian ethics, where the focus of the moral implications is on the intent of the action instead of the consequences. This is in opposition to utilitarianism, where the focus is placed on the outcome and intent is pronounced redundant. Our law system tends to lean more towards Kantian ethics, having defined borders, and making judgments based on intentions (e.g. manslaughter receives less time in prison than 1st degree murder). By this logic, collecting wild specimens for the trade is justified as the intentions of it hold no malice, with the aim not to destroy marine environments, but to bring their beauty into aquaculture. However, Kantian ethics should not be used solely, and instead we need a mix of different ethical viewpoints. It is also very difficult to look at the situation through utilitarian ethics, because it is very difficult to judge the standard of life and suffering of something like a fish compared to a human, and even more difficult for something like a coral, for which we cannot confirm sentience. However, through utilitarianism, we can make reasonable judgments based on human joy and suffering. If coral reefs went extinct, the 500 million people that directly rely on them would be displaced, the suffering from this action arguably outweighing the joy of the 1 million households with one of these tanks. However, it can be argued that the hobby is not the leading cause of coral reef destruction, with the more prominent culprits being global warming and ocean acidification.

This is exacerbated by the fact that most corals, especially stony reef-building species such as acropora,montipora,and seriatoporaare widely aquacultured due to their rapid growth rate. The corals which cannot be aquacultured or maricultured tend to be the most slow-growing and those incapable of asexual reproduction or have poor survival rates after fragging, such as the elegance coral, scolymia, cyarinaand acanthophyllia. However, it remains that there is a constant growth in the popularity of aquaculture, and an expansion in the corals which are able to undergo the process, outbalancing the ones which cannot. This is a somewhat similar case with marine fish. Common species to see in marine tanks such as clownfish, banggai cardinals, and surprisingly seahorses are now mostly tank bred. However, it remains that the majority of fish and almost all invertebrates save for a few (peppermint shrimp, anemones, cleaner shrimp, maxima clam) are still collected from the ocean due to being difficult to tank breed. Despite this, the animals collected are usually not endangered, and still have a healthy wild population, as rarer animals will be protected by organisations such as CITES, and receiving a permit to collect those species will be difficult at best, as well as countries which want to conserve their habitats, which can be seen in the recent Indonesian coral export ban due to illegal harvesting.

Another viewpoint of corals entering our hobby can be seen as protecting them from the increasingly bleak changing ocean conditions, and preserving them, with hope of restoration if wild populations disappear. Also, whilst coral reefs provide income and food for many, some of that is either collecting corals for the trade, or mariculture/aquaculture. The aquaculture industry is already worth $5 billion, and projected to grow even further, providing jobs for many. I agree that collecting wild coral and fish have a negative impact on the environment, but not to a great enough extent if regulated and done in a controlled enough manner to outweigh the jobs which it supports. It would be better to switch more to mariculture and aquaculture whenever possible, even if the costs are slightly higher, but as a whole, I believe that the collection of marine organisms for the trade is ethically justified.

Temporary beauty – knowingly collecting organisms doomed to die?

There is another ethical problem with the collection of livestock. That is, some marine species simply don’t fare well in our enclosed ecosystems, lasting for a few weeks or months, often below half of their expected lifespan. Even more than arguing about the quality in life difference in our enclosed ecosystems, this problem asks if there is any value in the life of a non-sentient organism?

One of the major group of animals which almost always die within a month in the hands of hobbyists are the non-photosynthetic corals. Unlike normal corals, their lack of zooxanthellae will dictate that their survival is completely based off of regular feedings of plankton. Large polyped NPS (non-photosynthetic coral) corals usually fare slightly better within our tanks, requiring delicate feeding of their mouths at least once every two days with meaty foods such as brine shrimp and mysis, putting them on the brink of starvation. Corals like this include sun corals, black sun corals, cup corals and dendrophyllia, often incredibly attractive to an unaware hobbyist due to their intense, bright, and attractive colours. In another league of difficulty, however, are the small polyped NPS corals, which include species such as the chilli coral (Nephthyigorgiasp.), dendronephthya, wire corals, lace coral (Stylastersp.) and many species of gorgonia. These animals are classed as “filter feeders” due to their constant consumption of small plankton, primarily phytoplankton and fish/oyster/lobster eggs. This means a huge demand of a food supply to be constantly available within the aquaria. Most often, either the food is too expensive, unavailable in the needed quantities, or cannot be fed to the corals regularly. Some corals such as the blueberry sea fan (Acalycigorgiasp.) may require upwards of 10 target feedings with a pipette every day. Even for people with the money and supplies, this amount of organic matter can seriously damage the water quality, elevating the nitrates and phosphates to the point where the coral may slowly recede and die. Even further, these corals such as dendronephthyaare very difficult to identify to their subspecies, and little to no information is given on their diet, meaning that a hobbyist would have to feed a slurry of foods, hoping that one of them might trigger a feeding response, which is detrimental to the water. All of these result in these corals being classified as a hair’s-breadth away from impossible.

We see a similar case with many “oddball’ invertebrates. Filter feeders notoriously struggle in aquaria, and bivalves are no exception. Except for maxima clams due to their zooxanthellae, bivalves, such as green-lipped mussels, thorny oysters, purple tiger scallops, electric flame scallops all have atrocious survival rates. The same applies to filters feeders such as colonial tunicates and sponges. There are also invertebrates such as sea slugs which are extremely poor candidates for our tanks. This is due to their diet of sponges, which in themselves are extremely difficult to maintain. Furthermore, each sea slug only usually consume a small handful of sponge species, and, even with the most common sea slug species, we are not sure of which specific species they consume. This makes rearing them an extreme case of trial and error.

Despite these factors, these animals are very regularly collected for the hobby. The reason for this is due to their extremely bright colours and unusual characteristics which makes them particularly susceptible to new hobbyists allured by the ignorance to their needs and survival rates. Therefore, the matter of whether collecting them boils down the question of if their lives have any value apart from being the centrepiece of our aquariums for a few months at best. This is extremely difficult considering that we are not sure of their sentience. However, I believe that it is ethically incorrect to import them in such large scales. The joy of having one of these organisms in aquaria is almost balanced by the sight of it slowly withering to nothing. Thus, one of the only benefits of collecting these specimens is for research, and for a small proportion of the coral trade. And so, I would argue that the biodiversity they offer, for there is a joy of preserving natural habitats outweighs the economic benefit, which is not very great. I conclude that these can be imported, but better on a smaller scale, reserved for research and expert level hobbyists who dedicate their time on finding out what makes these organisms tick, in an effort to find out how to make them more widely available.

Conclusion

The reef industry is growing and bringing along with it more widely available specimens which anyone is able to purchase. Before doing so, please be educated on the endeavours of keeping many of these organisms, including looking after the water just as much as the organisms themselves, and the sustainability and sourcing of the specimens. Though aquaculture is on the rise, it is still important to think about actively reducing the amount of wild caught specimens, in order to preserve this delicate habitat. In doing so, we can preserve its beauty for many centuries to come. There is currently a marine tank with clownfish in the biology corridor. Please do have a look (although at the time of writing this we are currently experiencing a cyanobacteria bloom), and please do not put your hands in the water without permission, as I have hopefully explained how important water quality is, and feel free to ask any questions.

Bibliography

[1] https://www.grandviewresearch.com/industry-analysis/reef-aquarium-marketreport

[2] https://www.researchandmarkets.com/reports/5553132/global-reef-aquariummarket-by-product-by- end?utm_source=GNOM&utm_medium=PressRelease&utm_code=xjbcps&utm_campaig n=1672670+-

+The+Worldwide+Reef+Aquarium+Industry+is+Expected+to+Reach+%248.4+Billi on+by+2027&utm_exec=jamu273prd

[3] https://www.researchgate.net/figure/Major-importers-and-exporters-of-marineornamental-organisms-The-major-importers-black_fig1_6365009

[4] https://en.wikipedia.org/wiki/Deamination

[5] https://www.vedantu.com/question-answer/by-which-process-ammonia-isconverted-into-urea-class-11-biology-cbse-5f4825ee55e8473a852c68a1

[6] https://doi.org/10.1016/S1546-5098(01)20005-3

[7] https://www.frontiersin.org/articles/10.3389/fphys.2010.00134/full#h4

[8] https://www.sciencedirect.com/referencework/9780123694003/encyclopedia-oftoxicology

[9] https://www.mercersec.org/sites/default/files/webform/fair_application/180/Microorga nisims%20for%20nitrite%20and%20nitrate%20removal.pdf

[10] https://www.cell.com/trends/microbiology/comments/S0966-842X(18)30024-6 https://www.wqa.org/Portals/0/Technical/Technical%20Fact%20Sheets/2015_Copper. pdf

[12] https://edis.ifas.ufl.edu/publication/FA165

[13] https://www.pwrc.usgs.gov/eisler/CHR_33_Copper.pdf

[14] https://cdn.dwi.gov.uk/wp-content/uploads/2020/09/23151717/chlorine.pdf

[15] https://www.jstor.org/stable/25038016?seq=3

[16] https://doi.org/10.1577/1548-8659(1975)104%3C800:CMIF%3E2.0.CO;2

[17] https://www.marine.usf.edu/reefslab/documents/evol_ecol2007/MullerParker&DeliaCh5_rev.pdf

[18] https://www.livingoceansfoundation.org/wp-content/uploads/2015/04/U5-CoralReproduction-Background.pdf

[19] https://algaeresearchsupply.com/pages/how-do-coral-get-their-zooxanthellae

[20] https://pubmed.ncbi.nlm.nih.gov/12917223/ [21] https://www.jstor.org/stable/35400?searchText=clownfish+anemone&searchUri=%2F action%2FdoBasicSearch%3FQuery%3Dclownfish%2Banemone%26so%3Drel&ab_seg ments=0%2FSYC-6294%2Ftest_segment_2&refreqid=fastlydefault%3A4254768947ac510c722bb7daa5b6f4d2&seq=7

[22] https://doi.org/10.1016/0022-0981(94)90019-1