Fishboy Hilbert’s no bullshit evidence-based guide to freshwater aquaria
(NOTE: this guide is work in progress - I would appreciate any sort of feedback given to me, and we are currently working on an infographic to summarise all this information)
Taking care of an aquarium can be made easy, but one must know the biochemistry. Buying a fish from your local fish store (LFS) is probably cheap, but keeping one healthy and happy would require a lot more effort and money outside of just getting a dechlorinator.
I’m gonna keep this short and simple: if you intend to get a fish, and you want it to be happy, these are some key points I will highlight that will prevent your fish from kicking the bucket within a few days. Read this through and it will spare you a lot of heartbreak.
Fishkeeping test
Test your understanding here: https://forms.gle/cN2UNbwuv6VDcWaHA
Highlighted points
Understanding basic chemistry
A knowledge in water chemistry is absolutely essential. In the wild, there are vast ecosystems in play. These ecosystems regulate everything from oxygen, to food, to everything else. However, any typical home aquarium can only scarcely attempt to reproduce the natural systems. Although fish can be hardy creatures, subjecting them to suboptimal conditions outside of their range of adaptability will ultimately lead to premature death, no matter the good intentions of the owner.
Many beginner aquarists find that their fishes kick the bucket within a few weeks, or if unlucky, a few days. Most of the time fishes can live far longer than this prescribed period. In other words, if an animal in an aquarium died, there’s usually a damned good reason for why, and not the common myth that fishes cannot live for long once they’re bought out of the LFS. It all depends on the care and understanding of the owner with water chemistry.
Fish stress is fish stress - there are no two-ways around it. A clear understanding on how to remedy an aquaria’s problem is by far the most effective solution.
General chemistry terms used in aquaria:
ppth - parts per thousand
ppm - parts per million
ppb - parts per billion
ppt - parts per trillion
pH - the acidity or alkalinity of water
GH/general hardness/hardness - the concentration of dissolved ions
KH/carbonate hardness/total alkalinity - the concentration of dissolved carbonate and bicarbonate ions
Salinity - the concentration of dissolved sodium ions
SG/specific gravity - the ratio of the aquarium water density compared to pure water
TDS - the total dissolved solids
Water volume and stocking
Water volume increases the buffer for mistakes in an aquaria. More water would equals to more dilution per unit mass of toxins in your aquaria. In the wild, the volume of water present is definitely much bigger than what an aquaria can hold - this is why many fishes can thrive in lakes and ponds. The vast amount of water allows for a higher stocking capacity. Stocking is defined as the livestock that you put in the tank.
In general, the fishkeeping community accepts a rule of one inch of fish per gallon of water. For further stocking instructions, it is advisable to look up online stocking calculators, such as https://aqadvisor.com/.
A very common mistake made by beginners is overstocking any aquarium. People see their LFS placing tens, if not hundreds of fish in a single small tank. This is far too many fish in a small aquarium. The fishes at the LFS are only there temporarily before they are sold. A much larger water volume is required for healthy fish, contrary to popular stereotype.
Solution:
Use a stocking calculator to ensure that your tank is not overstocked.Space
Space is required for fish to swim in. The stereotypical picture of a goldfish in a bowl is unacceptable. Not only is the water volume in a bowl far too little for any type of fish, let alone a goldfish, the fish has no space to swim around, and usually ends up idling in the centre of the bowl.
To give one a better idea, a healthy and happy goldfish would scavenge for food, and explore their environment constantly.
It is also required to take into consideration the adult size of the livestock. Fishes such as Oscars and Arrowana can start off as being very tiny, but can easily multiply in size. Unless it is a temporary setup, it is highly recommended to account for adult fish sizes before adding them into your tank, at risk of stress or having to re-home your fishes down the road.
Solution:
Ensure an adult-sized fish can do well in your aquarium.Fish tank shape
Fish tank shape is more crucial than what a lot of people think. Generally, fishes are more stressed out in spherical environments than rectangular ones. On the other hand, exotic pets such as jellyfish require non-rectangular aquaria, to prevent them from getting stuck at the edges, which can lead to fatality. As a general rule of thumb, it is advisable to research the requirements of your pet before putting them into their home, just as how one would scout an apartment before buying it.
Substrate (optional)
Substrate is optional for a tank, however it can provide a more natural and stimulating environment for your fish to be happy.
It is however, to be noted that one should aim for hard substrate that is not overly colourful or bears too much colour resemblance to the food that they feed. This can lead to fish ingesting said substrate, choking, and can subsequently prove fatal.
Solution:
If using a substrate, ensure that the substrate is either too large for the fish to ingest, or choose a safer, granier substrate such as sand.Feeding
Feeding generally should not exceed 4% of the fishes’ body weight per day, and any excess in feeds can lead to premature death from overeating.
To put this in perspective, a tetra from the LFS typically weighs around 0.14 g, while a typical molly at around 0.3 g. This means the amount of food given to a typical small tropical fish should, by general rule, not exceed 14 mg per day.
The general rule of thumb amongst aquarists is enough food for the fishes to complete in less than three minutes.
Solution:
Never overfeed your fishes. It is much more deadly to overfeed than to underfeed.Oxygen
Animals in your aquaria need oxygen. Oxygen is vital for the survival of any aerobic organism, and your aquarium’s pets are definitely not an exception.
Fishes and shrimp breathe through their gills. Unlike humans, fishes can generally only absorb oxygen dissolved in the water. This means that if your water isn’t oxygenated enough, your fish will suffocate.
Solution:
With the exception of a few fishes (i.e. bettas), a bubbler is almost always required for fish.Temperature
This point is closely linked to oxygen. The higher the temperature, the less oxygen can be dissolved per unit volume of water.
This is explained by Henry’s law. Partial pressure of oxygen in the air decreases as temperature rises, meaning less of it will be dissolved in water.
Tropical fish are more adapted to a hotter environment (think 28℃), while coldwater fish are more adapted to cooler environments (think 20℃). Tropical fish include tetras, danios, while goldfish are coldwater fish.
Solution:
Do not mix coldwater and tropical fish together. Make sure you do proper research on the type of fish beforehand.```Chlorine
This one’s a no-brainer. Most tap water around the world is chlorinated to keep it clean. Unfortunately, the dissolved chlorine also burns the gills of fish. Imagine your lungs being burnt - awful ain’t it?
In general, chlorination can be removed by letting chlorinated water sit for two days, or to use a dechlorinator.
Solution:
Add dechlorinator (typically sodium thiosulfate) to your water and wait for five minutes before using the water. Alternatively, you can let your water sit around for three days before using it.pH
Different fish come from different types of water, right? pH is generally not the biggest hoo-haa as compared to other factors, but a sudden shift in pH can result in what’s known as pH shock, which will lead to death.
pH outside of an acceptable range for fishes can lead to stunted growth, and increased susceptibility to disease. In nature, low pH is typically caused by tannins and humic acids being leached into the water, which both come from plant leaves. One can imagine that said acidic water can be found generally in forested streams, where leaf litter leaches these acids into the water. Contrastingly, high pH can be caused by presence of rocks such as limestone - the fishes that live in these waters include African cichlids.
To be safe, a typical pH value of 7.0 is usually fine for most fishes.
Hardness
Hardness, or general hardness (GH) is defined as the total amount of dissolved solids in the water. However, in aquaculture, typically only the divalent cations (with a +2 charge) are measured - reason being that these ions are usually the most abundant in the water, and play the most significance; this includes calcium (Ca2+) and magnesium (Mg2+) ions. Very hard water from taps would result in minerals depositing at the water pipes' lumen. Each species of fish require different levels of hardness to survive in.
Hardness is measured in French degrees of hardness (dGH), whereas 1 dGH equals to 17.9 ppm of divalent cations in the water. It is required for fish to build proper bones and other skeletal structures. Ideally the amount of magnesium ions should equal the amount of calcium ions in the water. Hard water is highly dependent on the environment where the water comes from, and tropical rivers with low pH usually have soft water, whereas rift valley lakes in Africa tend to have very high hardness, considering that they are surrounded by limestone.
Generally, hardness of aquarium water can be increased by adding limestone, crushed oyster shells, or the like. Some aquarists prefer to directly add magnesium sulfate (epsom salts) and calcium carbonate powder, however such a practice is not mainstream. Water softening on the other hand can be done using cation resins, or simply using reverse osmosis (RO) water during a water change.
12 dGH is generally considered the point between "hard" and "soft" water.
Carbonate hardness
Carbonate hardness, otherwise known as KH/total alkalinity, is defined as the concentration of carbonate and bicarbonate ions in the water. A high KH resists a sudden pH drop, which, if too extreme could induce shock in the fish.
KH can be introduced into an aquarium system by calcium carbonate, a component of oyster shells. This is why some aquarists add oyster shells into their aquarium. As calcium carbonate is not very soluble, little of it gets dissolved into the water. In order to raise the pH, some aquarists prefer to use crushed coral, which would similarly raise the pH and KH of an aquarium.
Nitrogen
One of the most highly overlooked key parts with beginner freshwater aquarists. Nitrogen is a key ingredient in amino acids and life, as they form part of the building blocks such as proteins. In the aquaria, animals will defecate and release waste into the water. Unlike humans, fishes literally have to swim in their own waste, which in certain forms can be highly toxic.
Undigested fish food, decaying plants, fish waste, or any other non-living organic matter in the aquaria is quickly converted into ammonia by bacteria and fungi. Ammonia exists dissolved in water as ammonium (a cation), and the names are used interchangeably. Ammonia is acutely toxic in the aquarium and can burn your fish.
Ammonia is nitrified by ammonia-oxidising bacteria, mainly in the genus Nitrosomonas, and rarely Nitrosococcus and Nitrosospira into nitrite. These three genus of bacteria use ammonia as an energy-source and dissolved oxygen to make water and nitrite. Nitrite is toxic to aquarium inhabitants, as it halts oxygen exchange into bloodstream, making the animals suffocate.
Lastly, nitrite is further nitrified by nitrite-oxidising bacteria, mainly in the genus Nitrobacter, and also Nitrospina, Nitrococcus, and Nitrospira into nitrate. Similar to ammonium nitrification, this process requires oxygen but does not produce water. Nitrate is a lot less toxic than ammonia or nitrite. However, it can cause stunted growth in aquaria animals, harm their reproductive system, and reduce their lifespan.
Nitrate is removed in aquaria by water changes. Other ways of removing nitrate is through live plants, algae, and or denitrifying bacteria, which will be discussed later.
One should always aim for an ammonia and nitrite concentration of ≤ 0.1 ppm in their aquarium. In a properly cycled aquarium and in wild ecosystems, ammonia and nitrite are almost instantly broken down into nitrate. A concentration of ≤ 40 ppm nitrate is considered alright in a freshwater aquarium, however realistically one should aim for 20 ppm and below. Marine aquaria require nitrates of ≤ 5 ppm due to the sensitivity of coral to nitrates.
Solution:
Cycle your aquarium BEFORE adding any fishes. If you are impatient, use a biostarter to kickstart the nitrogen cycle.Denitrification
Denitrification is performed by denitrifying bacteria in an anaerobic (oxygen-deficient) environment. Denitrifying bacteria typically consist of a very large range of bacteria phyla, including Pseudomonas sp., Bacillus sp. and others.
Denitrification typically involves stripping nitrates of their oxygen to meet the metabolic needs of the bacteria, and in the process producing nitrogen gas and water.
Typically, denitrification can be encouraged in a tank with deep sand beds, where the bottom parts are oxygen deficient. They can also be encouraged in certain filter media. Denitrifcation is a vital part of the nitrogen cycle in vast ecosystems; however, in an aquarium with high nitrates, consistent low percentages of water changes should be established, not a full reliance on denitrifying bacteria.
In the marine fishkeeping hobby, some aquarists have found that dosing vodka (containing ethanol) provides an inorganic source of carbon for denitrifying bacteria. However such a practice is not mainstream in the freshwater community.
Filtration
Filtration can be classified into three categories - physical, biological and chemical filtration. Filtration is REQUIRED for almost all tanks. Chances are, if you are planning on stocking fish, filtration is a definite must.
Physical filtration is the literal removal of insoluble debris in the aquarium water. This includes fully digested waste in the tank, otherwise known as mulm, or other forms of particulates, known as detritus.
Biological filtration is the use of bacteria in the tank to break down toxins. Such bacteria would include the nitrifying and denitrifying bacteria previously mentioned.
Chemical filtration is the use of chemical agents to remove toxins from the water by precipitation, ion exchange, or to convert them into a biologically inert (harmless) form to the fish.
Generally, everyday filtration takes on a few forms - the sponge filters, hang-on-backs (HOBs), undergravel filters, internal filters, and canister filters.
Sponge filters are pieces of sponges usually fed with an air current so that they act as both a bubbler and a filter simultaneously. The air that is pushed into the central of the sponge filter creates lift. Lift creates current in the water so that water flows into the sponge filter. Sponges are created with surface area in mind - which allow for nitrifiying bacteria to thrive. Occassionally, a sponge filter can get clogged with detritus - this is generally harmless, however, for aesthetic reasons, some aquarium hobbyists wash their filters. IT IS VERY IMPORTANT TO NOTE NEVER TO WASH FILTERS IN CHLORINATED WATER, which will kill the beneficial bacteria in the filters. Usually, a small amount of tank water is siphoned and the sponges washed in it, and the siphoned water discarded subsequently.
Hang-on-backs (HOBs) are usually placed at the side of the aquarium, thus their name. They work by inspirating water from the aquarium into the filter, before dropping it out. A significant advantage of HOBs is that they are easier to maintain as their parts are outside of the tank itself. In addition, the distance that the water has to fall from the HOB exit to the tank can agitate the water, in the process oxygenating it. Some aquarists put sponges inside HOBs as filters, while others use special media such as splintered glass to create maximum surface area for bacteria to thrive in. In certain occasions, an aquarist may choose to add chemical filtration media such as activated carbon into a HOB to remove medication from the water. A downside to HOBs are that their exits are typically close to the inlet, making filtration inefficient as water processed by the HOB is "re-used".
Undergravel filters are powered by lift that can be generated from air or an internal motor that generates water currents. As the name suggests, they require a substrate - usually gravel - to function. Undergravel filters usually have two parts, one part that is installed under the substrate, and another part that is above the substrate. The lift in the water draws water underneath the substrate in the lower component before it is expelled out from the upper component. This exploits the gravel's high surface area for bacterial growth, and if set up properly can turn an entire tank's bottom into an active, optimised filter. The downside of undergravel filters is that they tend to accumulate a lot of mulm and detritus, and vacuuming may sometimes be needed to clear it out for those who are particular about having "squeaky-clean" looking aquaria.
Internal filters are machines which are completely submerged under water. They are typically powered by an underwater motor that draws water in, puts it through a cartridge and expels it. The downside of internal filters is that the cartridge may have to be changed regularly, depending on the aquarium setup, and it would be relatively troublesome to do so. Additionally, internal filters can be used to generate current in the water, which is required by certain organisms, especially clams which are filter feeders and require fast water to deliver detritus to their mouths.
Canister filters or more commonly referred to as "canisters" draw water out from a tank into a separate setup, usually a box-like piece of equipment containing trays. Each tray is usually loaded with media to encourage bacterial growth. Upper trays may be responsible for physical filtration, medium trays for biological filtration, and lower trays for chemical filtration such as by ion-exchange resins. Canister filters are generally regarded as one of the more advanced equipment in hobbyist aquaria, and can also fetch the highest prices.
Solution:
It is absolutely necessary to have some sort of filtration in a tank. Ensure that some are installed.Incompatible fish
Imagine being locked up with a lion in a cage. Not the most pleasant experience eh? Aquaria inhabitants are generally classified with temperament. Temperament is essentially how likely that inhabitant is going to beat other folks in the aquarium.
Solution:
Always check up the temperament of your fish before adding them to ensure compatibility.Salinity
Water salinity is measured by parts per thousand (ppth). For 1 ppth of sodium chloride in water, it is equivalent to 1 gramme of salt in a total of 1,000 grammes of saltwater.
Freshwater is defined as < 0.5 ppth of dissolved salts.
Brackish water is defined as ≥ 0.5 ppth and < 30 ppth of dissolved salts.
Marine water is defined as ≥ 30 ppth and < 50 ppth of dissolved salts.
Briny water is defined as ≥ 50 ppth of dissolved salts.
Freshwater fishes cannot survive in marine water, and marine fishes cannot survive in freshwater. Ensure that research is done properly before stocking. However, certain fishes such as mollies, guppies, eels, mud snails, green crabs and salmon are euryhaline. This means that they can survive in both freshwater and saltwater. In spite of this, it must be noted that eels and salmon migrate to different salinities in the wild to breed. This means that a pet owner for these exotic fishes would need to switch the salinity of their tank periodically to ensure a healthy fish.
If one decides to put a molly in a saltwater system, drip acclimatisation is required. Most LFS sell and breed mollies in freshwater (their natural habitat is actually brackish water). In order to prevent shock by sudden changes in salinity, drip acclimatisation relies on slowly replacing the water that the fish is used to to the water in the tank. This also accounts for other factors such as pH, amongst other things. A sudden change in water parameters will shock your fish, and can compromise their immunity.
Solution:
Ensure that the salinity of the fish is researched beforehand. Never put a saltwater fish into a freshwater system and vice versa, unless they are known to be able to live in both, and use drip acclimatisation if so.Water movement
Water movement is another usually overlooked point. Livestock such as bamboo shrimp and clams require fast water flow. As these organisms are filter feeders, they require water current to bring detritus to them. Low water currents will starve them - OVERFEEDING IS NOT THE SOLUTION.
In addition, hillstream loaches require fast flowing water as well. These fishes are usually found in fast-flowing streams that have water coming down from mountains.
Contrastingly, bettas, especially male bettas require slow flowing water. This is because they have been bred into fancy versions with abnormally long fins and tails, which impair their ability to swim in fast flowing water. Fast water will in turn stress out the fish, as it would be required to move constantly to keep up with the flow, literally.
A fish that is not used to fast water and is placed in fast water can be seen hiding behind ornaments in the tank all the time. This is usually a sign something is wrong.
Water speed can generally be modified typically in conjunction with a filter (i.e. an internal filter).
Solution:
Ensure proper water movement for fishes. It is possible to create a tank that has regions of high flow and low flow, but this depends on your set-up.Research, research and knowledge
Knowledge is the only way to advance your aquarium. This article only covers the bare basics of fishkeeping - there are many other topics such as fish illness, even more advanced water chemistry, and so on - and this is just for what has been documented. Fishes are a very diverse group of organisms, each organism having its own specific parameters. It is fully the owner's responsibility to ensure that they are providing what they can for their fishes.
Every good tank is unique - each with different filters, and thus slightly varying chemistry and so on. However, what bounds successful tanks together from failed ones is how fishkeeping knowledge is applied to the tank. Not every problem in fishkeeping has the clearest solution, and it is up to you, the owner, to problem-solve to make your pets as happy as reasonably possible.
Happy fishkeeping! Have an attempt at the quiz set to solidfy your understanding, and feel free to contact me if you have any questions.