One Gallon? Only a Betta. Most anything that's small enough for a 1g is to active for one. A micro-tank can be absolutely lovely though if you plant it really well, get a rams head snail to keep waste down, and pick out a really pretty Betta.
External power filters are always better than any other kind of filter. The worst filter of the lot is the undergravel filter because it does not remove any poisons from the tank but stores them in the gravel from where they can poison the whole tank and kill all the fish if you have one power black out or a plug gets pulled out by accident.
It is best that all fish have a filter besides Betta fish. Betta fish don't need filters cause the filter pushes them over with their big fins. Goldfish should have a filter on there tank because they are often overfed. If you have a filter you won't have to change the water as often. The only fish that shouldn't have a filer in captivity are Betta fish.
no because male betta's are really aggressive to other betta's which plakats are male's. but female betta's can stay with other females. don't try to, one of your betta's are going to end up dead.
other Betta fish and the bigger fish.
Male Betta splendens fight with other male Betta splendens so the answer is most other fish will not fight with a Betta in the same tank. To try to list every species of fish here would be impossible.
becuse thay bite other fish
yes, currently most of all the betta fish come from china. they are found in little ponds with other betta's.
No. Betta fish will attack each other no matter the sex.
Male Betta's are solitary. They cannot be placed with other fish. That's why they are known a Japanese fighting fish. They will kill other fish for territory.
Yes, Betta Fish are extremely aggressive and they will most likely kill your other fish.
yes but only if yours is very hurt by the other betta fish.
There are over 20 members of the Betta family that I know of. They are all small fish and all have the same labyrinthine breathing system. None of them have the magnificent finnage of the common Betta splendens though. Other relations of the Betta are all of the other Anabantids including the Gouramies.