Do you guys leave your shrimp and crab molts in the tank?

Crab molts yes. Shrimp molt no just because its big and always ends up stuck to teh MP10

If I can get to them without ripping up the tank then yes, my Cleaner shrimp likes to shed his behind all the rockwork so it's impossible to get to. Where as my big zebra hermit shed his near the front of the front of the tank last night so I removed it. I don't like leaving stuff to rot in the tank.

Not usually... My crabs/shrimp typically molt behind the rocks... That and I'm lazy. If you have a tank larger than 10g I honestly don't think it makes a difference in water quality.

thats y we have a cUC?

The previous 2 molts I removed, but because of where they were. Just yesterday my scarlet molted again but its wedged underneath some rocks, and even with a pipette I can't get it out...just am kicking up sand and stuff onto some pissed off corals...so i'm just going to let it contribute to the tank :-)

Besides, whatever ends up dissolving will be useful in their NEW shell!

I saw a hermit molt in the front of the tank before lights out last night and was like oh that's interesting I'll fish it out tomorrow. The next day it was gone. If your CuC isn't eating your old molts you should probably think of beefing it up.

My CUC has always ignored molts, as have the fish. I've left molts in and never had an issue; tank sizes were 34 and 65, currently 125.