Slugs showing up in my newly cycling tank

[IndianaReef]

I have been cycling my 40 gallon (150L) tank for about a week now in which I bought about 4kg of live rock and 5kg of dry rock. In the past week spot algae on my glass has been forming, slugs have started to appear, and hair algae. Looks very alive to me! Is it acceptable to add a few crabs and snails to my tank as my nitrate has fallen to 0, my ammonia is dropping relatively fast, and my Ph is almost at 8.4 (8 right now). Only asking because it seems like there is a lot of life already in there and wouldnt mind a clean up crew ddoing the dirty business for me. Additionally, I made the mistake of pouring my crushed coral substrate in after my water was already in the tank, and now the water is a milky colour. I am going to do a 50% water change, but are there any other methods to stop this from happening (I did prewash my substrate). Thanks

 

[laverda]

Wait until your ammonia and nitrite are zero. Nitrate does not need to be zero and usually will increase as your ammonia and nitrite decrease. Filter sock, filter pads or floss should help remove the cloudiness.