Nitrite level during Fishless Cycling

[Dimitri]

Hi,

I`m at day 26 of a Fishless Cycle of a 20gl tank, my Ammonia is getting reduced from 2ppm to 0.25pmm in less than 12 hours, my Nitrates are at 20ppm but my Nitrites are far above 5ppm and are not reducing. I have already done several large water changes during the last three days, this temporary reduces my Nitrites but they quickly rise again above 5ppm. I keep adding Ammonia on a daily basis to stay around 2ppm.

What`s the best way to proceed during this stage of the cycle? Do I keep adding Ammonia and wait until the Nitrites reduce by itself?

Thanks for the information!

 

[Essjay]

The reason the nitrite level is so high is because you are adding too much ammonia. Each 1 ppm ammonia you add is turned into 2.7 ppm nitrite; 6 ppm ammonia becomes 16.2 ppm nitrite. At nitrite levels above 15 ppm, the cycle stalls, and as you can see it does not take much ammonia to go past stall point.

The way to get things on track is to completely empty the tank, then refill and add 3 ppm ammonia. Then follow this method https://www.fishforums.net/threads/cycling-your-new-fresh-water-tank-read-this-first.421488/ which was written so that if followed to the letter, nitrite can never get high enough to stall the cycle.

The first thing you'll notice in that link is that ammonia is only added when certain specific targets have been reached. It is not added every day.
You have already grown a lot of ammonia eaters so the first part of this method will progress quickly; so quickly that I suggest you test every day rather than every third day at the start. From your previous readings I would expect that you'll reach the first target the following day - that's ammonia under 0.75 and nitrite over 2. If this is what happens, add another 3 ppm ammonia - but if those targets have not been reached next day, do nothing and test the day after, and continue like this until the targets have been reached.
Once you have added this second 3 ppm dose of ammonia, follow the method, testing every second day, and wait until you have two zero ammonias two days apart. This is the second target. Continue testing every 2nd day and add 1 ppm ammonia whenever you have 2 zero ammonias 2 days apart.
The next target is any day the tests show ammonia below 0.25 and nitrite below 1 ppm. Then add another 3 ppm dose and test next day. If both are zero, the cycle has finished. If one or other is not zero, test daily until you get to ammonia under 0.25 and nitrite under 1 ppm again, then add another 3 ppm dose and test next day. Continue like this until they are both zero 24 hours after a 3 ppm dose of ammonia.

Then do a big water change and buy fish.



Have you tested your tap water for nitrate? You need to subtract the tap level from the tank level to see if any nitrate is being made in the tank.

 

[Dimitri]

The reason the nitrite level is so high is because you are adding too much ammonia. Each 1 ppm ammonia you add is turned into 2.7 ppm nitrite; 6 ppm ammonia becomes 16.2 ppm nitrite. At nitrite levels above 15 ppm, the cycle stalls, and as you can see it does not take much ammonia to go past stall point.

The way to get things on track is to completely empty the tank, then refill and add 3 ppm ammonia. Then follow this method https://www.fishforums.net/threads/cycling-your-new-fresh-water-tank-read-this-first.421488/ which was written so that if followed to the letter, nitrite can never get high enough to stall the cycle.

The first thing you'll notice in that link is that ammonia is only added when certain specific targets have been reached. It is not added every day.
You have already grown a lot of ammonia eaters so the first part of this method will progress quickly; so quickly that I suggest you test every day rather than every third day at the start. From your previous readings I would expect that you'll reach the first target the following day - that's ammonia under 0.75 and nitrite over 2. If this is what happens, add another 3 ppm ammonia - but if those targets have not been reached next day, do nothing and test the day after, and continue like this until the targets have been reached.
Once you have added this second 3 ppm dose of ammonia, follow the method, testing every second day, and wait until you have two zero ammonias two days apart. This is the second target. Continue testing every 2nd day and add 1 ppm ammonia whenever you have 2 zero ammonias 2 days apart.
The next target is any day the tests show ammonia below 0.25 and nitrite below 1 ppm. Then add another 3 ppm dose and test next day. If both are zero, the cycle has finished. If one or other is not zero, test daily until you get to ammonia under 0.25 and nitrite under 1 ppm again, then add another 3 ppm dose and test next day. Continue like this until they are both zero 24 hours after a 3 ppm dose of ammonia.

Then do a big water change and buy fish.



Have you tested your tap water for nitrate? You need to subtract the tap level from the tank level to see if any nitrate is being made in the tank.

Thanks for the information, this is very helpful. I did a 100% water change and saw my nitrites reduce to 0. I added ammonia to approximately 3ppm, 2 hours later my nitrites already increased again to 0.50ppm. I will check again tomorrow morning. I also checked my tap water, there are no nitrates in the water.

 

[Essjay]

The nitrate in the tank must have been made there. it suggests you have grown some nitrite eaters but then nitrite got too high and stopped them multiplying further. Taking it down to zero will let them start multiplying again, and the cycle should finish pretty quickly.