An Oscar can quickly grow to 14" and more given good conditions and good food. I would only consider another Oscar of similar size but at the same time I would be considering getting a larger tank. I have seen large 8'x2'x2' aquaria with large Red Devils and 10"Frontosa mixed in with 10"Oscars but since these fish species require totally different water conditions to flourish it is not something I would either do or recommend. HTH
If the tank is large enough. For rearing young Oscars a 50 gallon tank is about right for 5 fish.
Oscars are large and can be aggressive, their tank should provide at least 30 gallons of space per oscar, plus any space needed for any other fish. A minimum tank size of 40 gallons is recommended if you are keeping an Oscar. 10 gallon tanks are not for keeping large cichlids in. They are for keeping a few small tetras or other small fish. When it comes to Oscars and other similar fish, the minimum sized tank I would suggest is a 72" x 18" x 18" coupled up with a large power filter.
It all depends on how much other fish you have in the tank. Oscars need a lot of room so if there's tons of other fish in there it could cause problems. But if you have a couple it would be fine. If its a male Oscar its probably best you don't have them in a tank with any other Oscars. I volunteer at a pet store where they sell the fish so that's how I know this..
It depends on what size you have. You can have upto 1inch of fish for each U.S. gallon.
Jack Dempsey or Tiger Oscar
A small oscar can live in a 10 gallon for a short period of time. However, oscars are fast growers and can reach lengths larger than a foot so a larger tank would be required soon.
length and width for a 55 gallon fish tank
If you do the right thing by your fish it should not be dying. The basic rules for keeping fish are :- 1 inch of fish needs a minimum of 1 gallon of water (Oscars need much more). :- every tank needs a permanently running cycled filter. :- every tank needs to have at least 50% of its water changed every week.. Oscars need a temperature of above 75F and below 85F. One Oscar needs a properly set up 20 gallon tank. 2 Oscars can get by in a 30 gallon tank.
Sure, you can put it in a 20-gal. tank. It will probably do fine unless you put other fish in the tank that might eat it. The more water, the better for the fish. It may not look particularly aesthetic to have a little, bitty fish swimming around in a tank that size but, that isn't your concern, I presume.
betta fish like at least a 1 gallon tank (nothing smaller) > They can live in a community tank but with no other bettas.
you can put a betta in a 5 gallon tank
normal rule for fish in a tank is: For every 1 inch of fish there is 1 gallon of water