Nitrite keeps spiking... help! (Not a new tank)

[ChadOwens]

I have been having problems with recent nitrite spikes..... I checked the water this morning and everything was perfect... 0 nitrites. Then, i noticed my blue tand and pipe fish acting all crazy so I checked the water and the nitrite level was up to .25 ppm. This is the second time this has happened. About a week ago it spiked and I lowered it with water changes then it was fine for about 5 days. Then another spike today??

Note: this is a 12 nanocube

About 3 weeks ago I had a small carpet anenome die from a torn foot and wasn't able to remove it. Could this still be causeing the nitrite spikes.

What else might cause this?

I'm feeding frozen once a day
Live phytoplankton every other day (Could this be bad...spoiled?)
zooplex every other day

My pipe fish is doing fine now that the nitites are down but my blue tand is still breathing really fast and swimming wierd... will it be okay???


Any help with this would be great....

Thanks

Chad