Find their resting place. Mine always end up together on the same spot at some time during the day chilling for a couple of hours (lights on time normally). It's been like that for years. Whatever they do, they stick together in the end for a chat It could be a branch of driftwood or similar place where they feel safe. But it depends on the tank I guess.Is there an unspoken fishy rule that at least one oto must be hidden at all times? I don't think I've ever seen any of my otos out all at once!