I tell you, porthole catfish are great, they stay small and they clean up pretty well. They might need a little more food than scavenging, but they're not overly shy and will come out to eat. but if you have already have a couple of algae eaters, I dont' see how much scavenging you need in a such a small tank. It sounds kinda like overkill to me. Don't kill anything by putting too much in.