Guidelines For Selecting Ornamental Fish
The selection of the fish type that you would like to keep and care for is critical to other decisions you may have to make about size of tank and equipment.
Types of fish
There are really only a few categories of fish that you may want to choose from:
Tropical fish - these fish can be fish that live in salt or freshwater and the term is used to describe the water temperature i.e. warm.
Coldwater fish - these fish like the colder water temperatures and can be salt or fresh water fish.
Marine fish - these are fish that live in seawater. Most commonly marine tanks are tropical.
Freshwater fish - these fish live in freshwater and are usually the fish that you would find in inland rivers and streams of most continents. They can be as colourful as marine fish and yet less of a management commitment. Most freshwater fish in the ornamental hobby are tropical fish, which require a heater. The best-known ornamental coldwater species are goldfish or Koi carp.
Compatibility
The following factors should also be taken into account when deciding on the fish type you will keep. If you elect for a community tank then necessarily you will have to select fish which are compatible, and will not harass or eat each other. There are many really good texts and websites for obtaining this information.
Compatibility is also determined by the type of water that the fish like to inhabit. A take home message from here is that the fish determine their optimum water quality conditions - not you, the aquarist. So keeping this in mind, it is important that you don't select a mix of community fish that have completely different water quality needs. An example of this would be neon tetras (which like slightly soft and acid water) with black mollies (which like hard alkaline water). Now you may be advised that they will live together happily if you keep the pH neutral and the water moderately hard but, in fact, you have established conditions that keep all the fish under low-grade stress. Your fish may not die straight away but you will have reduced their life span dramatically.
Tank theme
Some aquarists will design their display tanks to a theme. For instance, the tank may be a representation of a section of the Amazon river. This allows the use of Amazonian plant species and it takes the guesswork out of selecting compatible fish species, because if they live together in the river naturally they should be happy in your purpose-designed tank.
Tank size
Be conscious of the fact that your fish will grow, so plan tank sizes for their adult size, not the size they are when you first buy them. If you have opted for a single large fish then you will need adequate tank space for the fish as it matures and becomes adult size. There is some credence in the belief that fish will grow in proportion with the size of the tank, however if you feed the animal the type and amount of food it requires for growth and maintain the optimum water quality, then most fish will keep growing to their genetic maximum.
By Dr Stephen Pyecroft - Last updated 19 November 2012
