I love Corydoras! I keep my four in a tank with my betta, shrimp, BN pleco, and hatchetfish. Filters/bubblers are not necessary, but should be used unless you absolutely can't. They do have a labyrinth organ, but they aren't as dependant on surface air as bettas. They need smooth gravel or sand (I think they prefer sand), because of their sensetive barbels. One of mine lost all of his whiskers before I switched to sand
. Cories are very fun. They are easy to breed, although I have yet to breed mine. Remember they need schools of 4+, though 3 is fine for a while. I have seen some awesome corydoras tanks on youtube!