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.
If the tank is large enough. For rearing young Oscars a 50 gallon tank is about right for 5 fish.
It depends on what size you have. You can have upto 1inch of fish for each U.S. gallon.
Yes can very well. Fish will only grow to the size of the tank so that means the Oscar will probably only get about 6 inches tops. And i would eventually upgrade to a 30 gal tank withing the next 6 months.
Jack Dempsey or Tiger Oscar
Any.
NO! Turtles are reptiles and should be kept in a vivarium never in an aquarium with fish. Reptiles and amphibians will foul the water and the fish will not survive.
betta fish like at least a 1 gallon tank (nothing smaller) > They can live in a community tank but with no other bettas.
length and width for a 55 gallon fish tank
probably a 50 gallon tank would be best.
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.
Neons
The only fish you can keep in a 5 gallon tank is one betta (Siamese fighting fish) on it's own as that is a very small tank.