I have a spotted cory and what I think is a green, or emerald cory cat. My spotted one just likes to chill and will scavenge around with the emerald when he feels like it, but the emerald will sometimes just start swimming around like crazy. He usually stays close to the glass and goes up and down and side to side and in circles and zigzags, you get the idea. Why? I'm not really concerned just curious. my waters fine and he's been doing this for a while. The other cory hardly swims around at all, only when he's hungery it seems.