Barbs are dieing...

Question
Ben -
I have had three barbs die in the last week. Tanks has been up for about two months. They all seem to loose balance and flop around for a day or two before going.  I would also say the dead ones have bulging eyes, and light color scales, maybe a slight body bulge too. they are not eaten, and the tank is not over loaded.

I've changed water weekly, about 4 gallons of the 30 gallon tank. The GH is about 60, KH has never moved from 0. PH 7, but the tank still shows ( and aways had...) about 3-5 on the nitrite scale and about 40 on nitrates.

Thanks a TON - I hate to see this go on...

Answer
Hi Scott
I saw your question in our question pool.

It sounds like it's the nitrites affecting them.  What's strange is you showing such high nitrites along with high nitrates.  If the fish were looking a bit swollen before they died, as well as the bulging eyes, that sounds like dropsy.  It's an internal infection, caused by a variety of things, but usually poor water quality is the root cause of it.  Start doing daily water changes until those nitrites go down to 0, and additionally your ammonia should be 0 also.  Try to keep your nitrates under 20 ppm as well.  Once those parameters get to those levels, then resume the weekly schedule, and I would up that to at least 25% each week.  Are you also using a gravel vacuum to clean the gravel as well?  If not, I'd recommend that.  A lot of uneaten food and fish waste gets trapped down in the gravel.  And, how often are you changing out your filter pads?  It says on the packages to change them monthly, but they should only be changed out every 3 months or so.  At least once a month, get a bucket of used tank water, and scrub the filter pad in that with your hand to get the gunk off.  Most of your beneficial bacteria is going to be growing on the filter pad(as well as the gravel and decorations).  Also, here's a link for you that explains the cycle process in detail, in case your not familiar with it:

http://freshaquarium.about.com/od/startupcycle/Step_5_The_Cycle.htm

There's also some articles on there about ammonia and nitrite poisoning.  If you don't have salt sensitive fish in the tank, like cory cats, tetras, plecos, loaches, any scaleless fish, you can add 1 tablespoon of salt for every 5 US gallons.  That helps when there's nitrites present in the tank.  Nitrites prevent the fish from absorbing oxygen into their blood stream, and the salt helps them to absorb the oxygen.

Hope that helps and let me know if you have more questions.

Christy