Aquarium size is basically a question of what size fish population is desired. Beyond that, this article assumes the desire for an aquarium is the enjoyment of its aesthetic qualities, and not its maintenance requirements.
These two desires are factors that both have a direct effect on water quality and thus the health, happiness, and longevity of the wildlife. This article makes a point that, with regards to water quality, larger aquariums are better. There are other arguments for larger aquariums, such as avoiding stunted fish growth (certain species) and aggressive behavior, but these will be discussed in another article.
More time enjoying the aesthetic qualities of an aquarium and doing the least amount of ongoing maintenance necessary, is accomplished by proper aquarium setup, so water quality will remain as consistent as possible and easily maintained. Water quality, as it relates to aquarium size, basically refers to how often water changes need to occur to remove toxins, thus keeping fish stress-free. Stress can lead to illness and death.
Keep in mind, though, that no matter how large an aquarium is, if it is overpopulated, then the water quality will be difficult to maintain. As such, unless the filtration system is multi-faceted and/or expansive, a portion of the water will need to be changed out more often.
There are other factors, of course, when it comes to water parameters and healthy fish; the two main ones being proper temperature and proper pH. But aside from assuming that larger aquariums are less subject to change, the details of those parameters are beyond the scope of this article.
Basically, the rule to go by concerning water quality is that larger aquariums have a much greater potential for remaining stable. Whereas smaller aquariums are more susceptible to changes effecting the entire aquarium, larger ones are not, solely due to water volume. This all depends on a fish per gallon ratio. However, smaller water volume means smaller fish population.
The 1:1 Rule… is 1″ of fish per 1 gallon.
This rule should be thought of as a guideline and is most useful concerning small, commonly-kept community fish. The absolute maximum amount of fish length should be no greater than the total volume. For example, a 10 gallon aquarium should have no more than 10 inches worth of fish. With larger fish, 1″ of fish should be cubic inches rather than merely the length.
Also, keep in mind that gravel, rocks, driftwood, plants, filter, heater, etc. take up space and reduce the amount of water the aquarium will hold. A 10 gallon aquarium when fully stocked, might then only hold 9 gallons of water, so no more than 9 inches of fish should be added.
“Fish” are considered to be anything that produces waste, and so includes any animal species in the aquarium. Plants are considered non-aspect when it comes to waste production, because they filter waste rather than produce it as long as they are kept healthy and do not die off. Plant health is greatly a function of lighting, which is discussed further along in this article.
The only real exception to the 1:1 rule is, as stated previously, the filtration system is multi-faceted and expansive. A filtration system of this nature will need to be housed externally from the aquarium. The most multi-faceted and expansive of these setups enable commercial aquarists to grow fish intended for human consumption on a large and concentrated scale.
Much of the success of these commercial systems has to do with the physical removal of as much waste as possible before it decays into toxins. Discussion of these elaborate systems, even when scaled down for use with a home aquarium, is an advanced topic, and is beyond the scope of this article. But the principle behind them remains true of home aquariums. The most important aspect being, as previously stated, the physical removal of as much waste as possible before it decays and releases toxins into the water. Thus, it is good to choose a filter that easily accommodates removal of accumulated waste.
The best ways to ensure aquarium water quality are to:
- stay under the 1:1 fish per gallon rule.
- have an aquarium size large enough that more fish can be added later if desired.
- have a filter system that includes a filter medium with a large surface area that can be removed for regular rinsing.
- have a pump delivering a gph (gallons per hour) flow rate of total aquarium volume. This aspect is discussed in Filter Pump Flow Rate, below.
- have an assortment of plant species and lighting appropriate for their growth.
- have scavenger species, such as shrimp, to eat the uneaten food that gets past non-bottom-feeding fish.
- regular vacuuming of any exposed gravel with a gravel vacuum.
If all these things are done, the need for water changes should be less frequent.
Filter systems are basically composed of 2 things… a filter pump and a filter medium. There are many manufacturers that have these 2 things built into the same unit, and they are the common choice for smaller aquariums. The 2 most popular types of these filter/pump units are canister units and hang-on-the-back units. Another type is the under-gravel filter. These three types, are compared in a little detail further along.
A filter system is required to keep the waste in the water flowing through the filter medium which will become inhabited with beneficial bacteria that convert ammonia (toxic) to nitrite (more toxic) and then to nitrate (less toxic than either). For more info on this process, read The Nitrogen Cycle.
Ideally, the water changes should really only be removing mostly nitrates. This is accomplished by physically removing as much of the wastes as soon as possible, as stated previously, before they break down releasing toxins into the water.
Without a filter, the beneficial bacteria will only be present in the water and on any surfaces in the water. Filter mediums are very porous, and thus have a lot of surface area in a small space. The entire surface area will become inhabited by beneficial bacteria. Also, the filter medium is in direct contact with the flow of water and so it will trap waste, e.g. uneaten food, fish wastes, and plant matter. This waste should be removed from the filter medium, otherwise it will decay and go through the nitrification process, which is a natural process; but waste is best removed to reduce bioload.
Bioload is the sum total of wastes undergoing the nitrification process. Keeping bioload at a minimum is beneficial to both plants and animals. As bioload accumulates, water quality becomes unbalanced, which can harm fish and inhibit plant growth. This is why it is so important to choose a filter where the filter medium is placed somewhere easy to access, so accumulated bioload can be easily removed.
Canister units sit outside the aquarium and the main appeal is that they can be fitted with different kinds of filter mediums, but accessing the mediums to remove the physical wastes is difficult compared to hang-on-the-back units. With hang-on-the-back units, the filter medium is easily accessed without turning off the filter, thus easy to remove and clean.
When it comes to filters, besides canister filters and hang-on-the-back filters, there is another choice, the under-gravel filter, although for most aquariums, it is the worst choice. Under-gravel filters use an air pump to move air up through tubes attached to an under-gravel filter system, which is basically a perforated tray the gravel rests on that provides under-gravel space. The water moves down through the gravel and up with the air bubbles through tubes in the rear corners of the aquarium. This is commonly a first aquarium filter setup. There are a few major problems typically with under-gravel filters.
Under-gravel filters utilize all the gravel as filter medium, trapping bioload there, which at first seems like a great idea if you are not over feeding and have plants. In theory, the plants will have all that fish waste directly delivered to their roots. But, in practice, so too delivered directly to the plant roots is a lot of dissolved oxygen present in the water flow. Generally, plant roots do not like lots of dissolved oxygen.
Also, the plants will doubtfully keep up with the constant supply of bioload. It will build up and need to be removed. A gravel vacuum can be used with partial success, but this is a lot of work, and if done too deeply into the gravel, can damage root systems. Also, plant roots will likely grow through the perforations in the tray of the under-gravel filter and inhibit water flow. The roots will also trap more bioload further down deeper into the gravel and beneath the gravel and even under the tray, where a gravel vacuum cannot reach. So, eventually, removing the physical wastes becomes impossible without dismantling the entire aquarium setup. This is also why under-gravel filters also make transplanting plants near impossible without damaging their roots.
When it comes to filters, keep in mind, more filter surface area is always a better choice… as long as the accumulated wastes are easily removed.
Filter Pump Flow Rate
Have an aquarium size large enough that it can house a filter with a pump delivering a decent flow rate.
A decent flow rate is considered to be at least 4 times the aquarium’s water volume per hour. For example, a 10 gallon aquarium will need a filter pump that delivers 40 gph (gallons per hour) through the filter medium. GPH is how filter flow rates are marketed by their manufacturers. When it comes to the above example, if the filter flow rate choices are 30 gph and 50 gph, go with 50 gph.
There are some exceptions to flow rate.
Aquariums that do better with higher flow rates:
- keeping larger fish.
- keeping more than the 1:1 ratio of fish.
- keeping reef organisms; water needs to be moving in all areas of the aquarium, simulating currents; this is because filter-feeders feed by straining suspended matter and food particles from the water moving around them.
Aquariums that do better with lower flow rates:
- keeping live plants, lower surface agitation helps hold in CO2, which plants need; and plants do not like to be moved by currents.
- keeping small fish, baby fish, or Betta splendens requires a very slow flow rate, and ideally, half (the left or right, not the top or bottom) of the aquarium should have zero flow rate.
Happy Fish is a big advocate that every aquarium needs a filter to maintain high water quality as easily as possible. For low to zero flow requirements such as with a betta, this requires a larger aquarium, even though there will only be 1 fish. For example, in order to achieve low and zero flow rates in different parts of a betta aquarium, the minimum recommended gallon size is 5 gallons. It is even easier to accomplish with a 10 gallon aquarium. For more info on keeping bettas, read Freshwater Tropical Species Profile: Betta splendens (Siamese Fighting Fish)… upcoming!
Choose a filter with a pump that has an adjustable flow rate mechanism so the gph can be fine tuned to what the fish and plants enjoy.
When it comes to pumps, remember to choose one delivering a gph flow rate equaling total aquarium volume.
Rinsing the Filter Medium
Rinsing a filter medium should only be done in water that was removed from the aquarium. Otherwise, municipal tap water, because it contains chlorines, will kill the beneficial bacteria in the filter medium. If the water used is not the aquarium’s own water, a lot of the beneficial bacteria could easily be removed from the filter medium.
In addition to removing wastes from the filter medium, a gravel vacuum can be used to suck up the uneaten food after it settles into the gravel. Also, keeping bottom feeders and scavengers, such as shrimp, will eliminate the need to constantly remove uneaten food. There will always be a need to use a gravel vacuum though, as most of the fish waste will accumulate in the gravel and otherwise decay.
Like bacteria, plants will utilize the waste, e.g. uneaten food, fish wastes, and plant matter. They are a living filter system in and of themselves, and they produce oxygen. This is important in aquariums that have lower dissolved oxygen levels, such as in a betta aquarium, the low filter flow of which will create little to zero surface agitation.
Plants require the right light conditions. An insufficiently, or over-sufficiently, lit aquarium will soon see those plants slowly die off. Plant species diversity can be of benefit to maintaining water quality consistency. Should water quality conditions become less than ideal for plant health, some species will survive whereas others might not.
Herein lies a perfect example of the benefit a larger aquarium holds. A group of plants of the same species, doing well in the aquarium, removing toxins and supplying oxygen, could suddenly die off. Some species, such as aquatic grasses, can decay very quickly. If not removed in time, the subsequent toxin levels can rise quickly in a small aquarium. potentially killing sensitive species quickly. If the same amount of these plants were in a larger aquarium, there would be more time before the toxins released from the decaying plants killed any of the wildlife. It is also possible that none of the wildlife would die before water quality could be restored. Keeping a diversity of plants rather than all one species can be a lifesaver, in addition to having the resiliency a larger aquarium affords.
Larger aquariums can accommodate a diversity of plant species even if they have different light requirements. There can be differently lit zones with plants in each zone having their own light level requirements met. But for smaller aquariums, an evenly spread consistent light source with plants that are ideally compatible with that light source is usually easiest. For more info, read, Easy to Keep Aquarium Plants.
This is the same reason why algae is kept in check by most aquarists. Algae grows in water high in nutrients, i.e. wastes. Algae is of no harm when healthy, and can actually be quite beneficial as it produces oxygen and reduces wastes. But the danger is that should a large enough amount of algae suddenly die off because it lacks the nutrients it needs to maintain itself, its rapid decomposition can cause a large amount of toxicity very quickly.
In conclusion, understanding the basics of providing for great water quality is essential to having a better idea of what sized aquarium is needed, so more time is spent enjoying aquarium wildlife and less time is spent doing aquarium maintenance.
About author and webmaster… Troy Boylan
Ecoculture Village Founder & President, Anthropology BA, Interdisciplinary Studies: Ethnobotany BS. Two things I think are worth anything at all… all things wilderness and ecoculture… and well, RPGs… and skateboarding!
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