Ok, I have a 20 gallon planted tank. 6 Green tiger barbs, 4 regular tiger barbs. I have two HOB filters. One rated for a 30 gallon, the other for 15 (Used when firing up the QT tank). I would like to put some Corys in there. I have shelter and a small cave dug out that I think they would find rather nice. Now I know corys like friends so I couldn't just get one or two, which means I'm probably starting to over fill this tank. Am I asking too much? If so, is there another bottom dweller I should look into?