Today I was doing my water changes and I decided that I wanted to switch things up and put CoCo in the bigger tank with new decorations and put Master Windu in the smaller tank with new decorations. Just so it was fair. (Sterilized all of the stuff first) Anyways I notcied Windu really perked up when I put him in there... He's swimming more in there and building a bubble nest.. I know it wasnt the water change because I had just done a full one 1 day before so I know it was clean.. Is it possible he likes the smaller tank better? It's a 1.5g.
I am just guessing, but maybe he was stressed out patroling the larger tank and "protecting" his home. :) I know my fish would freak if I put him in a larger tank than 3 gallons. It's good, though. :) that you found what makes him happiest.