Hi everybody. I change about 50% of my water every 10-14 days. Yesterday I did the typical cleaning - vacuum, new water, scrub algae, rince ornaments, etc. Last night I started smelling a rotten eggy smell. This morning before work, I smelled it a little more. And just now when I got home, i could smell it right when I came in the front door. Yuck! The tank looks perfectly clear and beautiful as it always does the day after cleaning. Fish are happy, water crystal clear. Fish hungry and beggging for food. But what is that smell!?? Thanks!!