I've had my betta for about a month now - after a rough start he has been doing great and has been very active and eating well. He has been in a 2.5 gallon non-filtered tank and has thrived in there. On Saturday I moved him to a 5 gallon tank (gave my 2.5 gallon away to a friend who was keeping her betta in a tiny bowl). I have not added the filter (a little afraid of how the whole nitrogen cycle works and don't want to kill my fish).
I also have a new heater for this tank, which keeps the tank slightly warmer - he was at about 78F in his old tank and in this new tank he's at about 80F. Yesterday was a warm day here and his tank got up to 84F, which I think is too hot, so I unplugged his heater to let the temp drop a bit. I plugged it back in once it had dropped to 78F (took about 5 hours) and then it settled back to 80F once it cooled down in the evening.
Everything in the new tank is exactly the same as the old tank, EXCEPT that I added a terra cotta pot as a makeshift betta cave. Before putting it in the tank, I decorated it by using aquarium sealant as glue and rolling it in aquarium gravel to decorate the edges. It dried overnight before I added it to the tank.
This morning when I got up I noticed that he was sitting on the bottom of the tank and not moving much. He has always been very active and comes to the front of the tank to "greet" people when they come to see him. He also would not eat this morning. He was swimming at the surface as if he was looking for food, but didn't seem to be able to see it. Very strange. He typically devours his food the moment it hits the water.
Now he's just sitting on the bottom with his fins clamped. He swims straight up to the top when he needs air, then swims straight back down to the bottom again. I did a 50% water change this morning and added 1 rounded tsp of AQ salt (this really helped him alot when we first had him and he was behaving this way). I don't know what else to do for him. Should I take the pot out? Maybe it's freaking him out. Not sure. Has anyone else had a fish that behaved this way after doing so well?