Help ! Another goldfish in trouble

Question
Hi Chris,

I had written to you a few times before for help with my new tank.  I had 2 small comet goldfish in a 10 g. tank to begin with and they both died within the first 2 weeks.  I had been monitoring and changing water as per your instructions.  The ammonia level went slightly up (.25ppm) but everything else stayed ok.

Anyway, after the 2 fish died, I brought just one small goldfish (a ryukin I think).  He was very active when he came about a week ago (the only fish in the tank now).  I took the water from my aquarium to be tested and the pet store said it was fine.  I also tested at home every day and there was no ammonia or nitrites in the water.  In fact I never had any nitrites at all till now (which makes me wonder why).  I was feeding the new fish very small amounts of food once a day, and changing 25 % of the water every other day just to be sure.  He was eating and behaving fine until yesterday, when I saw him just hanging at the top corner of the tank almost on his side and I thought he was dead.  But he was alive and started swimming around.  He stayed fine after that.  This morning when I woke up, he was again hanging in the corner without swimming, and was almost belly up.  I turned on his light and he swam a little but stayed mostly in the top of the tank.  The area around his gills looks a little red.  I tested the water and it was fine.  Now he is mostly hanging in the top corner of the tank, not swimming but just floating there, on his side or back as though he's dead.  Every now and then he swims a little but not much.  I can't figure out what I'm doing wrong, and why is he doing this all of a sudden even though the water is ok.  Do you have any idea?  Should I take him to the pet store and see if they can treat him?  I don't want to see him die too.  Thanks.

Answer
Hi Bela;

Sounds like constipation and gas. It is more common in the fancy types of goldfish than the regulars. When they eat dry foods sometimes they eat too fast and/or swallow air. This causes air or gas to stay in their belly. They float upside down or on their sides. It can be fatal so he needs to eat foods that will help him expel his waste and get things "moving" again.

Get a frozen green pea and thaw it out. Peel off the skin and feed him little chunks of it. Don't feed other foods until he poops and swims more normally. I have found that frozen brine shrimp, romaine lettuce, and spinach works too. Give him any of these foods at least 3 times a week. It will help keep him from having so much trouble in the future since he seems to be prone to it as a young fish already.

Keep up the good work on his care. You're doing a great job!

At Your Service;
Chris Robbins