Nitrates reading before nitrite drops?

[fishfairy]

I am still in the middle of cycling my new 55g tank, but I am making some progress. Yesterday, the tank tested at 0ppm ammonia and around 5ppm nitrite so everything looked good. The nitrite level has been steadily rising while the ammonia was steadily dropping which is normal. Then I decided to test for nitrate just to see if I would get anything. I wasn't expecting much of a reading if I got one at all since I have not seen any signs of nitrite dropping yet. Surprisingly though, the nitrate tested at 40ppm! How is this possible since nitrates are produced from the breaking down of nitrites? Unless nitrites have dropped some and I haven't been able to tell..

Sorry if this sounds noobish. Although I've cycled before, I never did any of my own testing. I just went to the LFS to get my water tested. Now that I have my own test kit, this is my first time monitoring water levels exactly during a cycle.

[Purrbox]

First off, test your tap water. You may have high levels of Nitrates in the tap water which makes it look like your cycle has created more Nitrates than it really has.

Also some test kits will read Nitrites as Nitrates giving you a false positive when there isn't any Nitrate present yet. It should tell you in your instructions or on the Manufacturer's Website if this is the case. If you can't find out for sure, post which test you are using and we can help you figure it out.

It is possible for your Nitrates to start going up before you see a noticable decline in the Nitrites. Basically the Nitrites are being generated as fast or faster than they can be converted into Nitrates.

[fishfairy]

I recently tested my tap water, but I actually can't remember if I tested for everything or just ammonia. I remember it came up 0. I'll test again for nitrates to night to make sure. I know that my other tank stays between 20 and 40 no matter what, which is a little high so that would make sense.

And I am using the AP test kit like most people on here use.

EDIT: I did not test my tap water for nitrates, but I DID test the tank water soon after I put it in and nitrates were 0, so I know these are not from tap water..

[JRagg]

You said you nitrites were pegged at 5.0 right? If that's the case you wouldn't be able to see them really drop anyways. I could sort of gauge how high they were by how long it took the test to go purple.

Towards the end of my cycle (using straight ammonia) I tested nitrates and got around 80. I'm guessing you're about 3 weeks into the cycle now? If that's the case, then it's totally normal. It will still take a while to get to the point where your tank can drop nitrites. It will happen one day when you're not thinking about it. I went from over 5 down to about 0.25 in one day.

Good luck.

[fishfairy]

Actually I am only 2 weeks into the cycle but I seeded it from my previous tank to speed things up a bit.

Also, should I keep dosing ammonia at this point to continue to feed the cycle? It was at 0 yesterday so I dosed 1 ppm to make sure.

[JRagg]

Yeah, dosing 1-2ppm every day or every other day will be enough to keep the ammonia->nitrite bacteria going. That's what I ended up doing, and my cycle (not seeded) ended in about a month.

[Purrbox]

You have to keep adding some Ammonia each day or the biofilter that you've worked so hard to build up will start to die off. I'd recommend about 2ppm of Ammonia per day.