Nitrates won't go down

[djoseph10]

I have a 30 gallon that's been running for a couple years, with just a few goldfish and doing fine. I never tested the water much, but I started to recently, and the nitrates were high. In the past week or so, I've changed out probably 30 gallons of water, and the nitrates are still too high. I've checked my tap water, and there is no problem with nitrates in it. Anyone have an idea why the nitrates would stay so high? Nothing else seems to be off (nitrites, ph). I would just go back to not testing the water and not worrying about it, but I lost a fish recently and that is the first time in at least 18 months I've had one die.

Dave

 

[Tifftastic]

How high were they when you first tested and how high are they now?

 

[fishorama]

Do you vacuum the substrate during water changes? A lot of "crap" can be down in any substrate. You might try vac'ing say 1/3 of the bottom at a time. How high are you talking? 80ppm or more (eek!) & you need to be careful not to change more than 10-20% at a time...but you also have to do them more often. I say that because drastic change in osmotic pressure can hurt or kill fish (look up old tank syndrome).

After you get it down around 40ppm or less nitrate you can do larger, less frequent WCs.

 

[SantaMonica]

Tricky way to get more filtering:

Looking for a temporary quick fix? Then don't clean your glass. That's right. The periphyton that grows on your glass absorbs lots of nutrients (that's what makes it grow), so by letting it stay there and get thicker, you remove more nutrients out of the water.

 

[FreshyFresh]

Dave, if you change 50% of the tank's water, nitrates should be lowered by 50%. I'd measure for nitrate, do a large water change (75%+), then repeat the measurement.

Also very common to not do the nitrate test properly with the API master test kit if that's what you are using.

 

[OrionGirl]

Other options to verify your test is accurate...since you know your source water is low, try mixing half tap water half tank water, and test. You should see half what you get from straight tank water. If not, tank nitrates may be higher than the test kit can return accurately, in which case changing out small increments of water over the course of a week isn't going to make much of an impact. Do you have a HOB filter? If so, try adding a pothos or spider plant to the filter. It will help with nitrate export and be protected from the fish eating it.