Is this a "mini-cycle?"

[avelazcooo]

I just finished a fishless cycle of my 10 gal tank - got ammonia and nitrites to zero, nitrates to about 10. Did a large water change, treated the new water with Prime, and added 4 small harlequin rasboras 2 days ago.

When the fish were added the water was testing just fine - in fact, nearly identical to my fish store's water. Zero, zero, and 10 for nitrates

Now, however, nitrites are reading .5ppm. Nitrates are still just below 10. The fish have been zipping around as pretty as you please but seemed kinda slower today; not quite themselves, though still eating well and moving about.

I did a 25% water change and they are much happier.

Is this normal? I was surprised to see so high a spike in a "cycled" tank.
Should I continue to do daily testing and water changes?
Are my little sweeties in danger??

Thanks!

 

[jm1212]

sometimes tanks are not very stable right after the cycle ends, and you encountered some of this when you added the rasboras. if you do a WC right after the cycle ends, it may disrupt the bacteria, and that couldve been the reason for your little mini cycle. it sould be gone either tomorrow or thursday since you did a WC

 

[khombre]

Just keep a close eye on your water parameters. If nitrites continue to show up then counter it with water changes. You can go up to 50%wc to bring those nitrites down to 0 level. Good luck