Jack Dempsey or Tiger Oscar
The rule of thumb is usually a gallon per fish, so six gallons would be good. If the fish are on the large side (like a goldfish), then a seven gallon tank would be ideal.
Danios or glofish would be a good fish to put in the tank. They are schooling fish which means you would need at least three and I wouldn't put more than 5 in a ten gallon tank.
A good rule of thumb is that you should have at least 1 gallon per 1" of fish.
Depends on the kind and size of the fish. You should also take in to consideration how large they will get at adulthood. A good rule of thumb to go by is 1 gallon of water for every 1 inch of fish. So for example: 3 2" fish should be in at least 6 gallons of water. To be safe I would put them in a 10 gallon aquarium.
It depends on the species of fish. 15 Guppies would need a much smaller tank than 15 Oscars would. A good general rule is for every inch of fish you have a gallon(4 liters) of water keeping in mind that your fish will grow.
Betta fish, guppies, tetras.
At least one gallon, any smaller, then: you would have to clean it allot more. The fish would be miserable of boredom, living in unsanitary conditions. And stores such as wall-mart, will be profiting from all the fish you replace. Just trust this coming from a guy with a 10 gallon tank complete with very happy beta, its worth seeing a pleased fish. Lastly, go to pets stores instead of walmart, follow the right instructions for your specific fish, and you and your fish should be good to go.
The fish are not bad together. But way to many fish for a ten gallon tank. You put one fish for every gallon. They will probly do fine but you will have to clean more.
Half gallon is miniature! it is cruel to keep a fish in a tank that size. I would definitely recommend getting a new, bigger tank. A 10 gallon would be ideal, fish options could be guppies (even though they breed like crazy) mollies, sword tails or platies.
Betta fish don't even think about goldfish they need 10 gallons each. If your bowl is bigger than 1 gallon a betta will do fine. Below 1 gallon get a ghost shrimp or snail
1 inch of fish per gallon so you about 18 but you will have the guppies eaten or the goldfish's fin bitten off as goldfish like to eat fish that are smaller than them (other than goldfish) and guppies are fin nippers so I would be careful or not keep them together good luck
I think about 8 or 10 would be fine, unless you have a VERY GOOD filter and lots of plants, in which case, maybe 20.