We have a 55 gal freshwater aquarium with an oscar and a pleco that are both about 3 years old. We've had them about 9 months. Originally we had a sand bed in the aquarium but switched over to gravel a little over a month ago. For the past couple of days the Oscar has started exhibiting strange behavior... lol. He is going crazy moving gravel all around the tank digging pits down to the bottom. He's constantly picking up gravel and spitting it out on these hills he's making. Because of this, he exposed a sharp looking corner of this slate rock I have in there. I went in to remove it and he attacked me, which he's NEVER done before. He swims away and hides whenever I stick anything in the tank (gravel vacuum, net, whatever). I tried sticking my big net in there which I know he's afraid of, to shield myself while I went for the rock again and he charged at it. Idk what's wrong with him. We do bi-weekly water changes and I checked the ammonia levels and such and it's fine. Any idea what could be driving my Oscar so crazy? I'm getting worried for my Pleco b/c though he's big enough that the Oscar won't dare try to eat him, I worry he's getting bullied and may be seriously hurt. He constantly hides under this log thing I have in there or behind this other rock where the Oscar won't bother him now. Help please.