Hydrogen Sulfide Smell

[PringlesLFE]

I have a 40G Breeder containing a pair of Honduran Red Points and a Jack Dempsey.
I use black Tahitian sand (Thin layer, just 20lbs for now).
Also have a filter bag of gravel from my old tank when I made the switch into this tank.
Ditched my Emperor system and am currently running a Fluval 303 canister.
(My order is activated carbon, sponge, biomedia)

A week ago I took out my fake plants and I've been doing 50% changes about 3 times a week for the last 3 weeks and 25% changes once or twice on top of that.

This is one of the decorative items I had in it, may be one of the larger problems because the inside is hollow all the way up to the head of the statue and I'm guessing it's a huge anaerobic spot.
http/www.petco.com/product/104118/PETCO-...C2%A9cor-104118

Also have one of these.
http/www.petsmart.com/product/index.jsp?...lmdn=Fish+Decor
and.
http/www.petsmart.com/product/index.jsp?...lmdn=Fish+Decor

Please help! My room smells like i'm in a swamp

 

[River Dog]

Has your sand compacted ? I know you say a thin layer, but the gasses given off smells a bit like you describe. As for your Buddah ornament, have you checked that you have no dead fish in there ? I had a large fake bogwood ornament bought for me and I noticed a smell and started getting ammonia readings. To cut a long story short, I found a dead clown loach and a dead BN plec that had got stuck in the ornaments branches and I have never used one since.