Yes it can. One gallon is the recommended minimum but many people keep bettas in smaller tanks without problems. My personal opinion is that any fish is happier if you provide it with a simulation of its natural environment. Bettas are happier in small tanks with plants, gravel and decorations than large bare glass boxes.
Yes. A goldfish can live without a filter. They may not live as long, but they do not have to have a filter, or a heater. I had goldfish in a five gallon tank without a filter for a long time. Hope that this helps.
no
u can use a aqueon 55 gallon filter
No, you cannot put these two fish together. In general you should keep Beta's alone by themselves, not even with other Beta's. They are mostly kept in bowls without a light, a heater or an oxygen line. The Beta will kill your guppy.
Some say they need a 5 gallon tank, but a 1 gallon tank should be ok if they are by theirselves.
get a bottle of seachem prime,a 5 gallon tank with heater and filter,and an API freshwater master test kit
yes you can it will be fine. i have experience :) haha
You may be able to use a very small internal filter with a 2.5 gallon tank. You can check with your local fish/pet store and they may be able to show you ones that would work for your tank
For a few days yes.
Clean filter
I would highly recommend it, yes
Yes, snails can survive without a filter in their tank, but having a filter can help maintain water quality and provide a healthier environment for them.