Akhtar
On a follow up to my previous post, I was working on both my Mother and Father in Laws tanks yesterday (water change, testing Ammonia/NitrIte/NitrAte etc) and noticed what could be described as "unpleasant musty smell like low tide at an estuary river" as mentioned before - but worse in the non-algae tank (M-i-L) rather than the algaed tank (F-i-L). Both tanks are fine, cycled etc. However both tanks have been running for 2+ years, so I am presuming the smell is just coming from the filter etc which have obviously been in heated water for that length of time.. Could be, might not be. Did a small water change (5%) in the smelliest tank and that seemed to help....
Just thoughts and observations...