Oscar Tiger in 20 gallon tank - Tropical Fish Keeping - Aquarium fish care and resources
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post #1 of 3 Old 11-14-2009, 12:34 PM Thread Starter
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Oscar Tiger in 20 gallon tank

I advised my husband not to get a Oscar Tiger Chichlid he wants for our 20 gallon tank. We already have 3 gouramis, 2 silver dollars and 1 rainbow fish in there. He says in a smaller tank, the Oscar will not grow as much, and it will not be a huge hassle. His source is a friend of his who has been keeping his Oscar like this for about a month. I'm dubious-- what should I tell him?
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post #2 of 3 Old 11-14-2009, 02:48 PM
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In my opinion, you already have too many fish in the tank. Silver dollars grow to six inches, and a 20g is not sufficient space for such fish. And an oscar attains 15 inches. I'll explain why this is not recommended even when the fish are young (small).

Keeping a potentially large fish in a small tank negatively affects its growth. And unlike humans, most fish continue to "grow" throughout their lives. But, this is not a benign process that results in a miniature version of the adult just because it is in a small space. What occurs is termed "stunting" which involves numerous health problems as the fish develops (grows). A defective immune system is one common result of stunting, which results in the fish contracting diseases and issues that it would otherwise be able to fight off. In addition to the physical size limitation of the small tank which causes considerable stress to the fish, there is a problem with the water chemistry in a small space; the fish is literally being slowly poisoned by not having sufficient water.

Young fish must be transferred regularly to larger and larger aquaria as they grow to allow for normal development. Unless you are prepared to provide adequate housing throughout the fish's expected lifespan, you should not consider acquiring such fish.

The silver dollars are already in this predicament, as their adult size of six inches, assuming they are able to live long enough, will require them to be in a much larger tank if they are to be healthy. And they are shoaling fish and should be kept in groups, minimum 5 or 6 but there is insufficient space in a 20g for even two. If larger aquaria are not possible, I would suggest trading the silver dollars for smaller fish that will be good companions for gouramis. The rainbow shark also attains six inches, and should be re-homed.


Byron Hosking, BMus, MA
Vancouver, BC, Canada

The aquarist is one who must learn the ways of the biologist, the chemist, and the veterinarian. [unknown source]

Something we all need to remember: The fish you've acquired was quite happy not being owned by you, minding its own business. If you’re going to take it under your wing then you’re responsible for it. Every aspect of its life is under your control, from water quality and temperature to swimming space. [Nathan Hill in PFK]

Last edited by Byron; 11-14-2009 at 02:52 PM.
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post #3 of 3 Old 11-14-2009, 04:02 PM
i agree with Byron 100% !!! with your current stock of fish, imho you need at least a 100 gallon tank.
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