Rainbowfish Aquarium
Rainbowfish Aquarium

Rainbowfish Aquarium

Aquarium size

One of the advantages with rainbow fish is that they can be kept even in comparatively small aquariums. The recommended aquarium size will of course depend on how many rainbow fishes you wish to keep and if you want to combine them with other fish. Also keep in mind that is it more difficult to keep the water quality up in a small aquarium. Many beginners start out with small aquariums since they think that large aquariums are hard to maintain, but the truth is that small aquariums are much trickier to keep.

If you have a 40 litre (roughly 10 gallon) aquarium, you can keep up to 15 rainbowfishes if you choose small species such as Pygmy Rainbowfish (Melanotaenia pygmaea) or Dwarf Rainbowfish  (Melanotaenia praecox). An 80 litre (roughly 20 gallon) aquarium can house an even larger group of small species, or up to 15 medium sized rainbowfishes like Boeseman's rainbowfish (Melanotaenia boesemani) or Duboulay's Rainbowfish (Melanotaenia duboulayi). A 150 litre (roughly 40 gallon) aquarium is large enough for up to 15 large rainbow fishes, e.g. Red rainbowfish (Glossolepis incisus) or Sepik Rainbowfish (Glossolepis multisquamatus).

Aquarium decorations

Create a lot of hiding spots for your fish, since this will make them fell less stressed and more secure in the aquarium. Live plants are recommended for the rainbowfish aquarium since it makes the fish feel at home and brings out their true colours. Plants like java moss are also appreciated spawning sites for rainbowfish. If you haven’t kept live plants before, ideally go for sturdy species like java fern and java moss. These species can adapt to most water conditions and does not require any special lighting or extra carbon dioxide. In most cases, the waste produced by your fish will be sufficient as fertilizer.

Hardness and pH-value

The recommended water conditions will depend on which species of rainbowfish you keep and obtaining species specific information is therefore always recommended. Some species are used to soft and acidic waters, while others need alkaline conditions to thrive in the aquarium. Fortunately, a lot of rainbow fishes are quite adaptable when it comes to water chemistry and many species can be kept in aquariums where the pH-value is 6.5-7.5 and the hardness between 0 and 100 ppm.


Try to mimic the natural environment of your specific species when keeping rainbowfish. Many species of rainbowfish can adapt to a broad spectrum of water temperatures since they hail from environments where the temperature varies a great deal. Rainbowfish have been found in waters where the temperature can drop down to 5 degrees C (41 degrees F), and species that live in shallow bodies of water exposed to the strong Australian sun can endure water temperatures above 35 degrees C (95 degrees F). Always research you particular species in order to find out their optimal temperature range. In the aquarium it is best to keep the temperature stable, unless you try to induce breeding by tampering with the water temperature. Generally speaking, 20-24 degrees C (68-75 degrees F) is recommended if you fail to identify the species of your rainbow fish. Increasing the temperature up to 28 degrees C (83 degrees F) may induce spawning.   

Organic waste

In order to keep the levels of organic waste down, suitable filtration must be combined with regular water changes. In a well established aquarium, biological filtration will help you break down ammonium and nitrite to nitrate, but the nitrate can only be removed through water changes. Ideally combine biological filtration with mechanical filtration, e.g. a sponge filter. Uneaten food should be removed and over-feeding must be avoided. Changing 25-35% of the water each week is a good rule of thumb, but it might have to be modified to suit your particular aquarium. An aquarium that is not heavily stocked might get by with smaller changes, while a heavy stocked aquarium might need a 50% change or more per week.

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