i would check the black bags before you start your 12/12 cycle. they might not be thick enough to block out all and could potentially cause hermie plants. wally world sells rolls black of 50ft 5ml plastic for about $6-8. its in the paint or arund the tool section. and your question about the clumps, dont mess with it. the only thing that will aerate the soil well is a good ratio of perlite.