Fishless Cycle - Nitrite Problems

[aclark]

My ammonia is converting just fine....pretty quick too. The problem I'm having is with the nitrites. I know they are converting because I am getting large nitrate levels in my tank; however, I cannot get them down to 0. I actually can't get them back on the test chart. I did a large water change today, 80-90% and they are still off the chart. There was a slight difference because instead of becoming instantly purple, the test slowly changed from blue to purple. I think they are coming down, but I thought a water change of that size would bring them into testing range. The nitrates came down from off the charts to about 10-20 ppm so the water change helped there.

What should I do?

• Should I just stop dosing ammonia and let the nitrites keep going and hope they come down?
• Should I do another water change to try and dilute the nitrites more?
• Should I continue to does ammonia so that the 'ammonia>nitrite' bacteria colony doesn't die? (I'm worried if I keep dosing the nitrites will just skyrocket again)
• Should I add some hardy fish to produce some ammonia and see where the cycle goes?

Couple notes. This is happening both in my 29 and 75 gallon tanks. I'm using Black Diamond sand. The 75 gallon was empty until last week when I added live plants. The 29 gallon had a goldfish in it, but its since died. It now has some fake decor and a few small live plants. Tanks are kept around 80F with 10 hours light (LED on 75 and CFL on 29). 75 gallon is using 2 Marineland 350 Magnums (one set up at the start, and the 2nd last week with the plants), and the 29 gallon has an AC50 on it.

 

[coralbandit]

The fishless cycle I learned from said to stop adding ammonia daily after nitrites were detected.
Once registering nitrites you cut ammonia dose in 1/2 and add every fourth day until both ammonia and nitrite are zero.
Caliban07 has good math on why this is so!

I believe he said 1 ppm ammonia is 2.7 ppm nitrite.
Example;
So if you added 2 ppm for like 5 days = 10 ppm ammonia which converted to 27ppm nitrites!!

 

[aclark]

Thanks. I haven't been adding ammonia everyday, more like every 3-5 days. I will stop adding ammonia (last time was Friday I think), and will continue to monitor nitrites for the next week or so.

 

[ScotJudd]

When I start a tank I dose 4ppm ammonia and then wait until it's dropped to at least 1ppm before adding any more. Nitrites, when produced will produce about 3 times the ppm than the added ammonia. This is a tricky stage because you are asking so much from the second stage bacteria. I personally water change to keep nitrite below 5ppm and add redose ammonia to 2ppm. I don't worry about nitrates, if produced, becoming too high but in diluting the nitrites you will in effectively reduce the nitrates as well.


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