Need some fish help.

[Ginevive]

Ahh, you have gotten bitten by the bug! I am just nuts about having tanks set up; it is really fun though, to set up new ones every once in awhile. Right now, I have set up our 4 tanks (125g, two 55gs, one 10g) and also have set up two for my sister, and another one for my dad soon.. so I don't just stop at tanks for myself. I even help my friend out at her pet store, cleaning and maintaining filters, stocking new fish, catching for customers sometimes (when I "owe her one" since she gives me rides to/from work..)
Hm.. for a 20-g, is it a long tank or high? If long, it would make an awesome "community" tank; swords, maybe some tetras, algae eaters once it is established and has algae. Personally, I love goldfish too; fancy ones, you could keep two in a tank that size. Comets though, they will definately outgrow anything smaller than a 55, and even that is pushing it..
I really like these freshwater puffers; I got one recently and he is very entertaining; his eyes move independently, he putters around the tank, really cute. But they are not a community fish..
If it is a high-styled tank.. maybe a few angelfish and bottom feeders (cory cats.)
Whatever you get, I highly recommend buying a Python brand siphon/hose. You can attach it right onto a faucet and fill the tank from it.. it makes life a LOT easier especially if you get larger tanks later.. I would never have these large tanks if it were not invented. The only time I lug buckets, is topping tanks off when a little water evaporates. Just don't forget and leave the water running and go outside or something; I almost flooded our house; we had water running out of the tank, into the dirt basement through a heating grate!!