Who Gives A Fish Forums

Driftwood can definitely funk things up. Boiling it before adding helps, but if it's been in there a while, might be time to replace it. Also, consider adding activated carbon to your filter for a week or two to absorb odors.

Man, I hate tank smells. Had a similar vibe last summer. Turned out my filter intake was clogged, so flow was weak. Cleaned that, added an airstone, and boom—smell gone. Maybe check your FX6 intake too?

Airstones help a lot with gas exchange. If you don't have one, grab a cheap one and see if it makes a difference. Also, how's your surface agitation? Low oxygen can make things smell worse.