Ammonia Spike while Fishless Cycling?

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Registered Member
Original poster
Feb 7, 2019
Hi, my name is Dally, and I'm new to the forums. I'm currently in the process of cycling my 55g Freshwater tank, and I've run into a bit of an issue...

So I believe I was nearing the end of the cycle. My ammonia readings were gone, and my nitrites were really low (.5ppm on API test kit) and Nitrates were present (near 20ppm)

I had been dosing at 2ppm ammonia throughout the cycle, and since I was near the end, I added a full dose of ammonia (2ppm) and waited.

Now I was gone for two days (a Friday and Saturday) so I had my mother dose 2ppm on each day to keep feeding the cycle She had done this before, and had helped me before, so I'm confident that nothing she did was wrong.

When I returned Sunday morning, I tested the tank... Only to find that ammonia had spiked (4-5ppm) and Nitrites had also spiked (way past 5ppm)

My question is... What did I do wrong? I thought I was nearing the end, as I had been cycling for almost a month and a half. Most forums say that it takes 4-6 weeks and I'm concerned.


AC Members
Jun 28, 2006
SF Bay area, CA
Did you ever see high nitrite before? I also have done your cycling method of 2ppm ammonia. I think this is just (finally) starting to cycle. How long have you been doing all this? Water changes?

It usually takes at least 4 or even 8 weeks to completely cycle a tank. Don't panic! You must be getting close!


Josh Holloway--Be mine!!!
Sep 1, 2003
Calif. SF Bay area
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I would not even bother measuring Nitrates till the Ammonia and Nitrites measure zero. It does not look like your cycle is finished yet.
What is your temp and PH?

Low PH and temp slows the cycle.
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Global Moderator
Staff member
Jan 11, 2013
West Falls NY
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Dally, welcome.

Tell us more about your setup? What type of filtration? Water temp? Substrate and decor?

If you've been dosing 2ppm/day for 6 weeks (without ever changing water), it's possible the nitrite spike has gotten so high, it's over-range high per what the API master test can read.

If nitrites get too high, the cycle will stall and just kind of sit there.

I would do a big water change and re-measure nitrites. I've been down this road before and it took two consecutive 50-75% WCs to get nitrites back on scale to where I could read them. The cycle was back on track pretty much instantly.


AC Members
Jun 28, 2006
SF Bay area, CA
Dally, do you have fish in the tank while you're cycling? That would require more frequent water changes & testing to keep them safe.

We have so many questions! But we need to know to help you.