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Cycling a new tank can be frustrating. Sometimes it seems as if it will never end. This forum member got answers from the forum community about elevated nitrite and nitrate levels.

"I have too high of nitrate and nitrite levels. I have done extensive water changes and my levels are still too high. They are reading at max levels even after a 30% then another 50% change both done within 4hours of each other.

I have been cycling for about 9 weeks and thought that things would be ready for new fish now. I started with danios and corys. I have a 55 gal and had originally added 6 danios and 3 corys. After 3 weeks I added 2 von rios and a 8 inch pleco. After another 2 weeks I added an additional 7 von rios and 2 corys. They were fine for a week and then they all died within the next week, one at a time. I waited 2 more weeks and then went to get some more fish. I had asked at the pet store I was in, what could be going on and they said that it was because I got my new von rios and corys at Pets Mart. I thought this might be the case so I went to my favorite fish shop and picked out 3 phantom tetra, 3 pencil tetra, and 3 emporor tetra. I also got a bottle of test strips, just in case, to check my water.

I then did a partial water change of 30% before adding the new fish. After adding the new fish I checked my levels. They are out of this world high on nitrate and nitrite. I talked to a friend who suggested I do another 50% water change. I did and the levels were still as high as they go. I tested my water from the tap and my R.O. unit. both are nutral in the nitrate and nitrite levels.

I do not know why my levels are so high after such a huge water change. I read that I could check my rocks, that some rocks are problems. I have taken them out and they are soaking in a bucket to test the water on, in a week. Is there anyone who can help me? What else can I do? What could be going on?"


May 7, 2008 at 4:41 pm
(1) Tim says:

If you have a friend with a cycled tank perhaps you could get a piece of his dirty filter media. If his (her) tank is cycled that media will be full of bacteria. Put it in your filter and the bacteria should continue to thrive and lower your nitrite levels. How’s your amonnia level?

May 10, 2008 at 1:09 am
(2) Maverick says:

Whenever you change your water this will elevate your nitrate and nitrite levels automatically as you are now stirring these things up.

May 10, 2008 at 11:46 pm
(3) Onatopa says:

I’ve just purchased a new Nano Tank and I’m going through the setup process… once again (I’ve had many tanks).

First and foremost, you speak of 9 weeks like it’s a long time and your tank should be ready to go. Not so fast. You need to understand the “cycle” a bit better. I’ll share a great link with you (see below). Read the page ‘carefully’ and then re-read again.
Just like your fish need care, so does the filtration system (which BTW you’ve said nothing about). Think of it that way.
So, the next thing is stop changing the water AND STOP adding fish.

During the cycling process, ammonia levels will go up and then suddenly plummet as the nitrite-forming bacteria take hold. Because nitrate-forming bacteria don’t even begin to appear until nitrite is present in significant quantities, nitrite levels skyrocket (as the built-up ammonia is converted), continuing to rise as the continually-produced ammonia is converted to nitrite. Once the nitrate-forming bacteria take hold, nitrite levels fall, nitrate levels rise, and the tank is fully cycled.

The link I’m sharing is here:

Hope this helps you out.

P.S. A water change does NOT increase your ‘nitrate’ levels…as stated in the previous comment. Nitrates and Nitrites are NOT the same thing. One you can have much more of before becoming toxic to fish (in fact, live plants will even use it). The other, nitrites, better be kept in-check and will be at zero (ppm) when the Nitrogen cycle is finished.

May 11, 2008 at 1:03 am
(4) Onatopa says:

I found another good link to the same discussion here:


I learned (or re-learned) that my live plants can directly use ammonia. My 3 large plants in this new tank look very healthy. Hopefully my sharks won’t eat them.

Keep the faith and good luck. As my grandfather use to say, “Patience is a gertrude (virtue)” :)

January 3, 2009 at 7:48 pm
(5) realtea says:

I had a similar issue, but with a much smaller but over-stocked but heavily over-filtered tank. After a treatment for disease, the bacterial in my filter died and my fish were suffering classic ammonia and nitrite poisoning. Despite persistent daily water changes over a number of weeks, the situation did not resolve it self. Then I bought a test kit (doh..) best investment ever. The pH of the water was around 5, meaning no new bacterial could grow. Unsure of the reason, but a bad of crushed coral in the filter cured the pH problem (now pH=7) and my tank is now cycling back to what it should be. Hope it helps….

August 5, 2012 at 7:53 pm
(6) Kate says:

I need help my fish two goldfish had fin rot a few werks ago I treated with melafix but didn’t help. I tested water and it was 8.5 ph so I did several water changes of 20 percent. Used a treatment to eeduce ph to 7.5. Treated with a fin rot medication again and then levels in tank approved and but now three weeks later happening again. Nitrate is nearly 80 after two small water changes but nitrite is virtually zero. I ve added culture every few days throughout and redosed with fin rot but one fish has blood all through his tail. please tell me which way to go now. Oh and I should say my tap water is very high in nitrate so should I use the prepared water they sell at the fish place instead ?

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