Betta fish are about the only kind of fish that can survive with no filter. They prefer still water or a very gentle current, so as long as you are keeping their water warm and clean (at least 80* F) they will thrive in a one gallon, unfiltered bowl. Change the water at least weekly to keep a one-gallon betta tank clean. Change more often in anything smaller (and it's not recommended to keep them in anything smaller).
Betta
Filters keep the water clean for the fish, kind of like we need clean air to breath properly. Also, filters keep the tank clean by (yep you guessed it) filtering the water. I hope this helped^^
it is always good to get some kind of filter for your fish, but natural ponds dont' always need one. the filters will keep out some bad bacteria though, and keep your fish healthy longer, and allow you to actually see them. goldfish are very hardy and can withstand quite a bit.
None, else, have 10 Foot shark :-)
No fish is best for a bowl, buy at-least a one gallon tank with filter, and you will clean it once every 2 to 4 weeks, a bowl will have to be cleaned every week. Also, your fish can swim better with more room, become less bored, and will be happier. If this is above your budget, fish is not for you.
Well there is not a whole lot you can do. I recmend (if you have a plant in the fish's environment) that you move your plant in the fish's direction to kind of get him movine
the answer depends on the fish species. if you didn't get the fish at a pet store, and found the fish in the ocean, keep it in saltwater. if not, use freshwater.
They have come up with new filters in the last year that want harm the fish, ready to use filters, that you don't have to rinse. But if you still get the old kind of filter where you have to open the bag of carbon and pour it in the filter then you willl kill them.
I would say gallons. Depends what kind of fish, but smaller than 10 gallons seems cruel.
Any tank that is at least 5 litres (1 gallon) in size, NO LESS.
It depends on what kind of plants in the fish bowl and what kind of fish. Pet stores sell decorative plastic plants as well as aquarium plants (real plants) for fish tanks. I think that there are even certain types of garden plants that may work in fish tanks, but that requires more research to make sure it is safe for your fish.
One of those freaky psychedelic frogs from S. America; no, two.