Ah, when you replaced the filter, you didn't keep the same bio-media? If you remove the filter media you kill the cycle. when you clean the filter, just take the bio-media (usually ceramic rings or something like that) and put it in a bucket of tank water, swish around and put back. Gotta keep the bacteria on it alive.
Learning a whole lot, thanks. Yeah I usually just replace the media as well which I believe is carbon. Juat tested the tank upstairs and well bot worth a sh**. Everything is all ove the place. Changing the water now(partial). Man this hobby is hard as hell.