Goldfish fin clamping

Question
I have a 30 Gallon orb that has been set up and running for at 3 months now and originally we had a sarrasa and a Wakin in it. We then bought 2 Shabunkins to go in then the sarassa started to clamp her fins and hang at the top of the tank then she started to hid then she died.  We cleaned out the tank and left it for 4 weeks then we bought a small black and gold goldfish.  Now about 6 weeks later one of the shabunkins is now doing the fin clamping and hanging at the top.  We do clean 50% of water every week.  Can you help?  

Answer
Hi Michala;

It may still be going through a break-in period. It affects fishes' breathing. Change 25% of the water right away and see if the sarrassa is feeling better. Also have the water tested for the levels of nitrite and ammonia. You could also test nitrAte, but there probably will not be any yet. It's different from nitrIte that you will find elevated during break-in. Here is more on the break-in period at my web page about it;

http://www.xanga.com/Expert_Fish_Help

If the fish still seems sick, there could be something else going on. Let me know how it goes.

At Your Service;
Chris Robbins