Yep. Three months exactly.
T Hizzle, I don't think tankmates have anything to do with this behaviour. Is the aeartion too strong? If it produces some kind of strong flow, it maybe stressful to him, and so he stays restless and swims around, like frantically in search of something. His usual behaviour is to stay motionless at the bottom, moving very slowly, and eventually going up for air, gulping it and back to the bottom again to its previous position. Check the air pump, if you have such, and slow it down. I wouldn't add any tankmates just to see if that is the reason.