Pretty simple, two much stuff and a crappy skimmer. Go get your bigger tank and the best skimmer you can buy watch your hobby grow.

Dave

I agree... you need a good skimmer for a high bioload. I use an AquaC Remora on my 20g... and it constantly pulls out nasty gunk. I always skim on the wettest setting too for maximum skimmate.

This is totally off subject but how do you have a mandarin in your 20g? Does it eat prepared foods?

yeppers, he eats anything,,, mysis, bloodworms, everything. pods... what is the best skimmer to put on my 20

I would simply gravel vac and do a few water changes...much cheaper than a SUPER WHAMMO SKIMMERZ0R.

try something silly like a 50% water change 3 days in a row, gravel vaccing each time.

I wouldn't consider those 4 fish A HUGE BIOLOAD like everyone is saying..give your heads a shake guys.

I would also try washing down the frozen food you're putting in your tank with pure water...might be getting phosphates or nitrates, or who knows what else from that. I found cyclopeeze was contributing to a huge problem in my tank. since I quit feeding it, my sand's been cleaning up and my glass doesn't get dirty nearly as fast.

also, try to get some readings for NO3 and PO4.

do you have a filter running with filter floss or a sponge? if so, either replace them or give em a really good cleaning in some waterchange water so the bacteria doesn't suffer.

and POSSIBLY, how old are the lights on top of your tank?

Everyone isn't saying the 4 fish is a huge bio-load.
It's the 4 fish and the clam, and the Finger Leather, and the Ricordia, and the conch, and the snails, and the crabs, and the Emerald crab, and the Feather Duster, and the BTA, and the various polyps, and the TONS of Zoos, not to mention the Live Rock (that wasn't mentioned).

Cheers,

yea i have about 20 pounds in there....