Fishless Cycle Help

[JoeH2014]

So I believe I'm in the latter part of my fishless cycle, but I'm having a problem with nitrites not going down. This morning I checked my levels, and for the first time, ammonia went from 3 ppm down to zero in 24 hours. But nitrites are still sky high, as are nitrates. The reason I'm concerned is because I've done two water changes already to lower nitrites specifically, because they've been off the chart for a few days. I've attached my latest test results.

What should I do? Continue dosing to ammo to 4 ppm? Should I do another 50% water change? Any help you could offer would be greatly appreciated. I feel like I'm close, but I don't want to over do the water changes.

Thanks everyone!

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[Masha]

This was my experience also, and seems a normal part of establishing the cycle.

You can consider dosing to less than 4ppm Ammonia as that is more than your filter is likely to need to process once the tank is stocked. That will help keep Nitrite spikes under control.

Some say that high nitrites can inhibit the growth of the Nitrite processing bacteria, so do as many water changes as you need to get Nitrite to a measurable level. It's perfectly normal for that to take several huge changes.

Be careful not to overdose prime, or whatever dechlorinator you are using.

Be aware this stage can take a while, as the Nitrate processing bacteria take the longest to duplicate.

So keep going, sounds like you are on the right track

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[JoeH2014]

Thanks a lot for your response, I appreciate it. I've also read that high nitrites could be an issue, so that's why I'm concerned. I think I'll do another huge water change later on then.

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[PNWaquarist]

I'd suggest dosing with 0.5 ppm ammonia for a couple of days and seeing if your nitrite level goes down. If not, then do a large water change.

The idea of too much ammonia slowing the growth of the nitrite-oxidizing bacteria is somewhat controversial, but it's clear that the ammonia-oxidizing bacteria in your tank are a strong colony and are working just fine. You could go without adding ammonia for a few days and they'd survive, but it's best to at least keep them happy.

When your nitrite levels fall below 0.5 ppm, you're likely near the end. Dose with 3-4 ppm ammonia at this point. If you have 0 ppm ammonia and nitrites within 24 hours, you're done.

 

[JoeH2014]

That sounds good. Thank you so much for the help!

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[mattcham]

If nitrites are over 1ppm, it can inhibit the bacteria that break down nitrite. It seems to make no sense but that's what most people claim. I would think that if nitrite is the bacteria food then more nitrite will accelerate bacterial growth, but this is apparently incorrect.

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[JoeH2014]

If nitrites are over 1ppm, it can inhibit the bacteria that break down nitrite. It seems to make no sense but that's what most people claim. I would think that if nitrite is the bacteria food then more nitrite will accelerate bacterial growth, but this is apparently incorrect.

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It sounds to me that there is a fair amount of debate on this. I happen to agree with you. I've followed the advice here and just lowered my daily ammonia dosing to 1ppm and will give it a few days to see where it goes. Given that I'm getting nitrates, and lots of it, I've got to believe I'm very close, but maybe not.