I've got an adult Red Tail Shark in a community tank with Cardinal Tetras, Zebra Danios, Bloodfin Tetras, Ghost Shrimp and a Pleco. Before I added the Cardinals and Zebras the shark would harass the Bloodfins. I took a que from Tyyrlym and re-arranged the tank to offer the shark a smaller and more defensible territory. He took to it immediately and now has claimed and guards the hollow base of the fallen tree in my 25 gallon tank (back right in the pics) and does not harass any of the other fish. Previously he had basically claimed the entire bottom third of the tank as his. Since the changes he's extremely mild mannered and his tail is BRIGHT red which leads me to believe he's happy with the changes.
If you're set against the Red Tail you might look at the Silver Apollo Shark (Luciosoma sp.). They don't get huge and are a schooling shark so you can have multiple in one tank. They are supposed to have less "attitude" than most other sharks although I've never had any so I can't speak from direct experience.
"The beauty of the second amendment is that it will not be needed until they try to take it." -Thomas Jefferson
Last edited by rgs1975; 07-21-2009 at 12:18 AM.