Lately, Zues, my beloved 6" pleco has been acting really wierd. Normally he is the life of the tank, swimming around, eating everything in sight, and occasionly picking a fight with my oscars or cats. If provoked, he will chase the instigator around the tank mercilessly. However lately, he has been moving around the tank really slowly, and will stay in the same position for a long time, which Is not like him. Also, he is letting the oscars bully him, and just keeps on hiding, which is also not like him. Normally, he practically inhales any cucumbers I drop in, but he has not touched the one I dropped in yesterday. The water parameters are fine, and all the other fish in the tank are doing great. What's happening with him?! Help!