Learn Aquarium Management

The three main categories of aquariums are:
• Fresh water
• Brackish water (mixture of fresh and sea water)
• Marine or seawater

These can be further divided into:
• Cold water aquariums and
• Tropical or warm water aquariums (i.e. reef aquariums)

Within the above categories, aquariums for fish can be divided by types:
• Peaceful community aquariums
• Aggressive or semi aggressive fish species
• Single species or 'specimen' tanks


Course Structure and Content

There are 10 lessons in this course:

1. Scope and Nature of Aquaria
2. The Water Ecosystem
3. Water Quality and Management
4. Equipment and System Design
5. Suitable Inhabitants for Your Aquarium
6. Fish Health and Diseases
7. Freshwater Tanks
8. Simple Saltwater Tanks
9. Maintenance
10. Breeding


Course Duration - 100 hours



Water Treatment

Reverse osmosis – RO is a form of demineralisation to purify water. With this process water is forced through a semi-permeable membrane that removes most of its mineral content - essentially producing pure water.

Distillation – distillation involves boiling water and then condensing the steam or water vapour back to pure water, this process leaves minerals and impurities behind in the boiling chamber.

Exchange resin units – in this process water passes through a unit containing certain resins designed to draw out specific chemicals from the water, leaving only pure water. For aquarium use, `mixed bed’ resins are ideal as they do not leave a chemical imbalance and result in a neutral pH of 7. The resins need to be replaced on a regular basis so this process can be expensive if water needs to be purified for large aquariums.


There are several ways pollution can occur in an aquarium:

Firstly, the water supply may have contained pollutants or contaminants before it was added to the aquarium, these may be from tap water treatment chemicals or other compounds dissolved in the water supply.

Secondly, chemical pollution can occur from the surrounding environment, for example the use of aerosols and sprays such as fly spray or air fresheners, fumes from heaters, paints or cigarettes can all pollute the aquarium as they dissolve into the water or are introduced through the oxygenation system.

Thirdly, pollution can occur from the use of certain equipment and hardware inside the aquarium - it can result from rocks or substrates containing toxic minerals, wooden items leaching tannins, use of decoration not intended for aquariums such as certain metals or plastic items, glues, paints and varnishes. Finally, pollution can be a result of the natural aquarium ecosystem itself and originate from organic wastes such as fish excreta, uneaten food and dying plant material or algae. These types of organic wastes in a well balanced aquarium ecosystem can be recycled via biological processes, the most important being the nitrogen cycle.

Nitrogen Cycle
The nitrogen cycle is vital to the success and maintenance of healthy fish and a well balanced aquatic ecosystem. Organic wastes such as fish excreta, food, plant material and dead algae are broken down during the nitrogen cycle from toxic ammonia to toxic nitrites and then processed into nontoxic nitrates by beneficial bacteria which colonise 'mature’ tank systems. In a newly set up aquarium these bacteria are not present in large enough numbers to carry out the nitrogen cycling of toxic wastes into nitrates. Over time, the Nitrosomonas and Nitrospira bacteria build up and establish a biological filtration system which carries out the nitrogen cycle at an efficient rate provided the aquarium is not overcrowded or overloaded with organic matter. This process of establishing the bacteria in the biological filter can take several weeks.

Overcrowding can often be a problem when starting a fish aquarium. Overcrowding can create a number of issues in the tank which may include behavioural fish matters, health concerns associated with pollution from dirty water, or unnecessary parasites present in the tank. Therefore, it is important to have in mind that the size and amount of fish, plants or ornaments present in the aquarium may or may not create a harmonious environment for those inhabiting an artificial tank.

Some of the problems associated with overcrowding can include:

  • Territorial fights among the fish
  • Disparity in the amount of food intake
  • Suffocation
  • Imbalanced nitrogen cycle and inefficiency among the bacterial colony responsible for biological filtration
  • Pump problems from a dirty tank
  • Diseases and so forth

Problems with overcrowding will depend highly on the temperature of the environment the organisms belong to. For example, cool water fish are often more sensitive to oxygen deficiency conditions as opposed to warm water fish. Cool water fish might show their discomfort by blowing bubbles at the surface of the water and attempting to breathe atmospheric air to compensate the depleted oxygen in the aquarium water.

Overcrowded fish may cause the death of one fish, which, in turn, may lead to parasitic problems. However, overcrowding does not necessarily mean the death of the fish or of any other living organisms in the tank, but it will undoubtedly be responsible for the vitality of these organisms by putting stress on the ecosystem.

Points to avoid overcrowding

  • First thing to do is to determine the requirements of each fish to be kept in a tank - some fish species are known to tolerate higher stocking densities than others.
  • Determine the size of the fish’s maximum growth - as a general rule of thumb, larger growing species should be stocked at a lower rate.
  • You will need to know the surface area of a tank - the water at the surface holds more oxygen and fish use the surface to breathe air.
  • You will need to know the volume of water in the tank - to accurately work out stocking density.
  • Consult your local department of fisheries or aquarium experts for advice on stocking densities for different species.

In a closed environment it is important not to overfeed fish. If you do, uneaten food will collect at the bottom of the aquarium and decay. In doing so, it will cause a rise in ammonia levels and interfere with the nitrogen cycle. Levels of bacteria may increase as decomposition takes place and this in turn will reduce the availability of dissolved oxygen in the water for the fish, since oxygen is used up in the decomposition process. There will also be fluctuations in pH with an overall lowering, and ultimately a build-up of nitrates.

To avoid overfeeding, some aquarists would suggest to not feed the fish for one day per week, though if you control the amounts of food given this is unnecessary. Food should only be supplied at a rate which the fish can consume within a set time frame. If you observe the fish eating this will give you a clearer idea. Many fish will have consumed all they are going to eat within one minute, and often as little as thirty seconds or less. Others, particularly species which feed at the bottom of the aquarium, may take several minutes. Once you are familiar with your fish's preferences you can give them an amount of feed which will be fully consumed within this time frame. Any extra will just end up decaying on the bottom of the tank.

It is better to feed most fish (with the exception of large predator fish), a small amount several times a day since this mimics their natural feeding habit in the wild. Predator fish, which usually only eat once in a while, may only need feeding once every two or three days but they will need to eat a larger amount. Try to vary the fish's diet and replicate what they would normally eat in terms of minerals and vitamins.