Carbon Filter = Ammnonia/Nitrites?

Monkey Man Zero

I have been cycling an 8 gallon Biocube with 9 lbs live rock and 10 lbs live sand. Levels were good:

Ph 8.4
Ammonia 0
Nitrite 0
Nitrates 10-15 ppm
Salinity 1.026 @ 78 degrees

I had a fish in my big tank get popeye so my nano became my hospital tank. During treatment, I took the carbon filter out of the cube.

Levels stayed the same and were great, even with adding fish food, garlic, and the meds.

I put the carbon back in today and ammonia, nitrites, and nitrate spiked within 8 hours.

I did a quick 50% water change and they have dropped some. I am currently just watching nitrite and is is at .5 ppm.

The only change was adding that carbon back in. Has anyone else seen a spike like this? I figured there is trapped bio material in the mesh of that filter and I have removed it.

chadf

You put the same carbon bag back in? If so all of the bacteria died and you put the dead stuff into your tank causing the ammonia spike and starting a new cycle.

Monkey Man Zero

That's what I was afraid of. Beginner mistake.

I've got the ammonia and nitrite down to .25 through water changes, so hopefully they will continue to drop.