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Fishless Tank Cycle - Help

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Hi all,

I'm well in into a fishless tank cycle - almost a month or more now.

Within 36 hours or so Ammonia reaches 0ppm from 4ppm; however, Nitrites linger around 0.5 ppm for an extra day before it reaches 0.

I assume then that the tank is not completed the cycle correct? Does Ammonia and Nitrite levels must reach 0 at the same time usually?

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Have you tried reducing the amount of ammonia by 1/2 and noting how long ammonia and nitrites take to reach zero? Or are you still adding ammonia at level to reach 4 ppm?
Is tank heavily planted? what is nitrate reading?
I haven't tried cutting the Ammonia to 2ppm and see if nitrites reach 0 at the same time, but i'll try that.

I brought Ammonia up to 4ppm as a test to see I have enough of the bacteria to bring it down to 0 and enough of the Nitrite converting bacteria...which apparently, I guess I don't have a strong colony of.
If I were you, I'd say it's time to add some fish. Choose some robust fish like white clouds to start. I'm sure you'll find you have very little, if anything, in terms of ammonia / nitrite spikes. Once they've been in there awhile, you can start adding other fish.
If it were me, I'd hold off a little longer before adding fish. I prefer to see my tanks convert 2-3ppm of ammonia in 12-24 hours. 4ppm within 36hrs could be within that same range tough. Reduce the ammonia and see how long it takes to reach 0ppm. As far as the Nitrites, it should be 0ppm period. It should not be detectable. Nitrates is the only toxin in your tank that should be detectable. If your heavily planted, this could be low. Impatience can cost you a little bit, or a lot so its up to you to save your pocket book.
If it were me, I'd hold off a little longer before adding fish.
Seems a little conservative, but that's just my opinion. I can't disagree with anything designed to increase the safety of the fishies.

Anyway, I mentioned white clouds because I had a surprising experience with them. My brother had an outdoor "pond" last year with hordes of white clouds, and no place to put them at the end of the season. I ended up keeping them in my quarantine tank for a few months while he readied an indoor tank for them. The big day came, and we moved all the white clouds to their new home.

When I got back to my house, I changed the water, with ice cold (but conditioned) tap water, and added a 1/4 teaspoon of ammonia to the 10 gallon quarantine tank, just to keep the biofilter going. Perfectly safe since there were no animals of any kind in there now.

Two days later, I just happened to glance over at the quarantine tank, and there were 20-30 white cloud fry swimming in there!

I couldn't believe it. They (or their eggs) had survived 50 degree tap water, and dosing with ammonia. Hard. Core. Fish.

I raised these stalwart fish to maturity and they now live at my brother's house.
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So Ammonia and Nitrite should both reach 0 at the same time?
Is this the first time you're seeing nitrite or have they risen and then fallen but you can't get it to 0?

Typically ammonia will start being converted to 0 within 24 hours of dosing first (this can take 2-3 weeks on average). Then nitrites show up; they'll spike and then after about 3 weeks on average they'll suddenly fall to 0. That's when the cycle is done.
Ammonia goes to 0 in 36 hours, and Nitrite takes another day, and eventually goes to 0. I was under the assumption that for a tank to be 100% cycled, the Ammonia when at 0 will also have Nitrites also be at 0 at the same time. Assuming that Ammonia was injected to bring it up to 4ppm.
Usually once the nitrite spike happens they fall to 0 and then yes typically ammonia goes to 0 in 24 hours and you don't see nitrite anymore. If the nitrite spike already happened but you can't get it to 0, have you tested PH lately? PH drops are common during cycling and if they drop too low the bacteria can slow down. Also when was the last time you did a water change? If it's been a while you might want to do a large one to restore buffers and minerals in the water, then wait until the next day and redose ammonia but only dose to 2 and see what happens in 24 hours.
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