Hello, I had an aquarium when I was a kid but the fish always died, and here I am trying again! Anyways, it started with a Betta, but I felt bad keeping him in a bowl so got a 20 gal aquarium. Now I want more fish (of course). So, I understand that Bettas can be aggressive, so I've been researching and decided I want corydoras and harlequin rasboras. I read that these are both shoaling fish, and like to be in big groups, so I plan on getting 6 corys and 6 rasboras. I have a large sponge filter with 2 sponges, and the filter that came with the aquarium. I am also aware of nitrogen cycle and am testing the water. My question, does this setup sound ok? If so, what kind of corys would you recommend? Thanks!