My tank has been up and running for awhile now. Have fish in it.... da da da....
I went to scoop out a victim of the filter and was overwhelmed with this gross smell. The tank is clean, did a 75% water change two days ago. I checked all the levels of ph, amonia, nitrate and nitrite. Everything is where it should be.
Any ideas on why it smells and what I can do to fix that?