I think one of the biggest problems with otos is the stress from shipping them. I bought a few and put them into a cycled tank that had been running for 4 or 5 months, and they all died. I just got 3 and put them into my tank that has been running for 2 weeks, and they're fine. The only difference was that the first batch was fresh into the fish store, and the second batch, from wal-mart of all places (i know, i know) I guess had been there for at least a week or two. They're doing great now. It seems if they have a little while to get over the stress from shipping and fatten up again, they do better. When you buy them from a fish store, ask how long they're been in stock. I think the longer they're been around, the better chance they have of surviving the move home.