Is it OK to have one fish in a tank?

there are fishes that are supposed to be alone in a tank, like a fighting fish, a flower horn, or an arowana. but i prefer fishes that can be placed with other fishes in a tank. i would love to watch a school of fish going to and from in an aquarium. ^__^

It depends on the fish. Some are perfectly fine with being alone, others aren't. You have to do research into the fish that you want to find out if they like to be in groups or not.

Almost all fish need at least two fish t be able to reproduce,(yes there are exceptions). If the tank is set up right (large enough and set up right) then you can have more than one Betta in a tank. Or for that matter the red tail catfish (that can get to be over 4 foot long) can be housed in extremely large tanks of ponds together with others of the same species. Look at the public aquariums that have many sharks that live in the big tanks. Yes some fish should be housed separate (or at least so that they cannot get to each other) such as the flowerhorn cichlid (which is a hybred cichlid frome two or mere different species of cichlids.

I can say it depends on the fish you will take car of. If its an arwana (i am not sure if i spelled it right), I think it is ok to have just one fish in the tank. I think its size depends on the fish tank itself so you need to adjust the fish tank depending on how your arwana had grown. But if its a goldfish or any other small fish4es, it will be adviseable to have more since it will also look nicer if there is a school of fish in the tank.

Yes its ok to have one fish in a tank specially if you a have an aggressive breed/type of fish like flowerhorn ciclids. They are very territorial and would fight if they are sharing a tank with another one. :-)

It's not bad to keep just one fish because there are fishes that are better off alone. Aggressive fishes e.g. flowerhorns or fishes that grow really big and eat other fishes e.g. red tail catfishes are usually kept alone in the tank. The tank looks lonely though, if you keep just one fish. Try schooling fishes like tetras, the tank looks happier.

I don't think it's bad. There are certain types of fishes that need to be isolated such as arowanas, oscars and the so-called "fighting fish".

It really depends on the type of fish. Some fish are 'sociable' and really do best in schools of 3 or more. Some fish, such as betta's are generally aggressive and don't always do well with other fish. Betta's sometimes can be placed with other fish, fish that are warm water fish and fish that won't nip at the betta's long fins, or the betta won't nip at theirs. So really, it depends on the fish as to whether or not they would be ok alone or not.

if the fish isn't filing for a complaint, why should it be bad for any fish. :)

If you are not getting a type of fish that schools, like neons, it should be ok. If the fish is used to being alone, it will be happy in the new tank. If it used to friends around, it might have problems. I put my male Beta in with my son's goldfish. They became friends. when we had to get rid of the goldfish because he got too big for our tank, my Beta acted SOOO depressed!

Well, it depends on which species you are getting at. Some species such as tetras are schooling fish so you would need to get at least 6 for them to feel secure and be confident, othewise too few or even a lone one will not do well (even if water parameters and temperature may suit the fish). Some like betta (Siamese fighting fish) are alright to be reared alone, but I personally feel that they need to be in a pair to be happy. Then again, the size of the tank it's living in also play an important role. Would you be happy alone in a small room or living in a spacious house?

I don't think its ok. Put some more fishes..