Weird, but expected?

[Kennyyoli]

I have a 29 gal gravel bottom tank that has been stocked and cycled for 2 years. A week ago, my Fluval 205 Canister I had on that tank had a complete failure. Motor area was smoking hot, and after cooling down, it wouldn't come on. I went to try and find a duplicate filter, and couldn't find one locally. I ended up buying a Fluval 305 Canister, and set it up on the tank, with the ceramic ring media from the 205 transferred to the 305. Unfortunately, the foam portions were a different size, and I couldn't use them.
I fired it up, and kept an eye on my parameters. My ammonia has been in check, but the past 3 days, my nitrites are sky high. I got the fish out when the spike first showed up, and they are at my sisters house, quite happy in her quarantine tank.
My question is two part. I did a huge water change (70%) yesterday, to get the nitrites down to .25 PPM. Ammonia was at 0. Within 3 hours, the ammonia was still at 0, but the nitrites were back up to between 3 and 5 PPM. I am assuming the ammonia is being taken care of the colony of bacteria that turn it into nitrites, but it seems I have lost the colony that eats the nitrites, and produces the nitrates. Since there are no fish to worry about, should I just leave the nitrites high to get the tank cycled, or should I still do some partial water changes? Also, it seems with the nitrite explosion that the ammonia eating bacteria have plenty to eat. Should I be dosing any ammonia as well,
to keep that colony fed?
Thanks in advance for the help!

 

[Pandicorn]

Well, It's been quite a while since I've cycled any tanks, so please don't take my advice 100%. If you have detritus in your tank, (any dead plant material, fish poo, leftover food etc.) I think you will be able to keep your dosing to a minimum.

Could you please list the fish you have as well?

This happened to me, but unfortunately I didn't have a QT tank and I lost 6 fish to a nitrite spike x(. Assuming your fish are safe, and have a home they can live in for a while, I would just let the mini-cycle take its course. It shouldn't take more than 2 weeks (Could be wrong on this one), and when it all stabilizes dose some ammonia, and test if it converts completely into nitrate in 24 hours. It's late at night and I might not have answered clearly, if you have any questions feel free to ask. Good Luck!