[MrBump]

OK...5 weeks into a fishless cycle on a 90 gallon aquarium. About 15 or 16 days in, the ammonia dropped to zero and nitrites spiked just as expected. I've dosed pure ammonia to 1-2 ppm every night. The next day after work the ammonia reads 0 ppm.

Here's what I don't understand. My nitrites have been in the 5+ ppm area since they spiked about 3 weeks ago (tested water is a bright purple with a slight pink in it). I've done four partial water changes of about 25% and not seen any change in the nitrite reading. Tonite, about 2 hours ago, I did a 75% water change. I just tested again and my nitrite reading is the exact same as the reading before the PWC. How is that possible?

The water temp is at 85 degrees with plenty of airation from an FX5 filter. I test my water straight out of the tap and it has no measurable nitrite.

I'm baffled. For what its worth I'm testing with a new API Master kit.

 

[dotbomb]

You likely had off the chart nitrite and it may have stalled the cycling a bit. Get nitrite down to 1-2 ppm and dose 1ppm ammonia. Wait until nitrite drops before adding more ammonia. You can easily go 3 days without adding ammonia. If after a few days nitrite is still at 5ppm then do a water change to bring it back down to 1-2 and dose 1ppm ammonia again.

 

[dotbomb]

I should add once you see nitrite converting you can ramp up your ammonia dosing. You just don't want to go above 5 on either ammonia or nitrite.

 

[DrTim's]

You let the nitrite get way too high. This inhibits the nitrite-oxidizing bacteria. To get the cycle going faster you need to do more water changes. You do not have to add ammonia everyday those bacteria will not starve. Once you get the nitrite down do not let it get above 5 ppm (3 is better).