AAARGH!!! Nitrtie spiking

[yvez9]

Here's the deal

I added 1 siamese flying fox yesterday and 3 glowlight tetras

I also removed 2 female bettas the same day

this morning, we lost power for a couple hours while i was at work.
I came home to find my aquaclear mini running dry, so it's been running dry for about 6 hours.
the aquaclear 150 managed to prime itself and was running normally.

anyway. Nitrite spiked, not that much, but still. i can clearly see the color in the test tube.

i did a 25% water change but still can't figure out how nitrite could spike like that with still my main filter running.

I have a sponge, some purigen and some bio-max in there.

a 150 is rated for a 30 gallon tank, and i have a 20 that is not fully stocked!
Ammonia is still 0 so i know the bacteria didn't die off.
my 50 gallon is perfect too

nitrite took forever to go down in this tank while cycling and now it goes back up at the first little problem

can anybody explain to me why nitrite would spike like this so fast?

 

[yvez9]

Wel
this morning nitrites are less than 0.1 so i guess it is not very harmful anymore.

I had put a spare aquaclear mini sponge in my 50 gallon filter in case something like this were to happen. am i glad i did!

i put the sponge back in the filter and overnight, the nitrites almost cleared

I'll check again later today and probably do an extra waterchange too.

i don't think any fish are dead though it's hard to see the tetras in the dark