I had never had a fish before I got my veil tail betta, Thor. He has suddenly become ill, and I'm really worried. I got him in April 2011. He struggled with fin rot while I was cycling his tank, but he recovered and was doing great for the last few months.
Monday was the first day that I noticed something was wrong. He is lethargic, has lost a lot of color, has clamped fins, and is spending a lot of time at the top of the tank. His abdomen (the area where his pelvic fins come out) looks bloated and tight. I don't think his scales are 'pine-coned,' although I'm not sure if I would recognize that in its early stages.
He lives in a cycled 5-gallon tank with a 25W heater in my office. There are no other fish or live plants in the tank. I treat his water with Amquel (2 drops/gallon) overnight before putting it in the tank. I change 1-2 gallons of the water every 1-2 weeks. I feed him Hikari betta pellets, 3 pellets per meal. He gets 3 meals on Mondays and Fridays, 2 meals on Tuesday through Thursdays, and no meals on Saturdays and Sundays.
I was out of town for a few days last week, but my co-worker assures me that she followed my explicit instructions for feeding him according to his usual schedule, and swears he did not get any extra food. We are friends and I think she would tell me if she screwed up. I checked his ammonia, nitrate, and nitrite levels on Monday--all were fine. He also ate normally on Monday. I changed out 2 gallons from his tank on Monday. Tuesday morning I fed him 1/4 of a peeled, thawed frozen pea. I haven't fed him since then.
Our AC was out in the office, and it's been really hot. His water temp has been running a little warm, like 78-82 degrees. I can't think of anything else that has changed (except I changed his carbon filter cartridge last week before I left town.) Those are the only things that are different.
Is there anything else I should be doing? I feel terrible seeing him so obviously uncomfortable and not knowing what to do. Thanks in advance for your help.