My cycle's been going well. My ammonia has always been safe.
Now it's reading at .5 (danger) a day and a half after the change.
During this change I pulled out the carbon filter. It was very gross, full of grey fluff, stringy, etc. All I thought think was, "ew, ew," and changed the filter.
I took the sponge and cleaned it in the tank water. Then I replaced it.
It is possible I've restarted my cycle? Are my fish at risk? It took months to get it where it was. But then again, I can't keep the same carbon filter in there forever.
Also, is the carbon poisonous to my fish if they touch it?