Nitrite spike

[gordo33]

I have a 36g tank that was cycled without fish. There is a sponge filter for BB. The tank has been cycled for more than one month. I had to move the tank so it was emptied moved immediately to new location and refilled wit tap water treated with prime. I dosed it with 5 ml of ammonia like I do daily to keep the BB alive. Since the move the nitrite reading are between 1.0-1.5ppm. I decreased the daily ammonia by half yesterday. Why would the nitrite level spike after a 100% WC? I have performed 30% water changes on this tank to reduce the nitrates without a change in nitrites. Any thoughts would be appreciated. Thanks

[diegote]

Have you tested your tap water?

[gordo33]

Not recently but I have two display tanks that I do water changes in 2-3 times a week that I test on occasion and do not have issues with nitrites.

[MendoMan]

It's common for a fish less cycle to take 6 weeks, i'd bet your cycle isn't completed yet.

[gordo33]

The cycle was completed after 5 weeks with ammonia and nitrites at 0ppm for 5 additional weeks until the 100 % wc when the tank was moved. I don't understand why the nitrites would stay elevated after 100% wc when there was no nitrite reading after 30% wc

[Kyla]

u sure u fed the same amount of ammonia?
wc was with the same temp water?
media did not dry out?
could BB living on the tank walls have died off and lowered the total # enough to make a difference?

[DJW]

How long after adding ammonia did you test for nitrites?

Fish add ammonia to the tank at a slow steady pace. In fishless cycling you dump ammonia all at once and create first a bottleneck of ammonia, and then several hours later there is a bottleneck of nitrite.

You didn't mention whether there was gravel or if its bare bottom. In a new tank a lot of the BB culture can be in the gravel instead of being all in the filter.