You may kill the shrimp, but you may also kill a lot of other beneficial critters.

I don't know about dim lights either. You want to keep lights on the coralline algaes. The algaes will also help to process waste. Turning light off will not kill of nuisance algaes like hair. Its just going to delay the bloom until it goes into your tank.

My suggestion is regular conditions and just skim like heck. Scrubb off any dead material. Its sometimes referred to as "liver." Water changes with water close to tank salinity (1.025) is good too.