I have a 20 gallon refuguim on my 75 gallon tank. It has been up and running for about 4 months. I notice today it has a bunch of algae grwing like a film on top of the sandbed, is there upkeep for this sand bed, do I need to pick this film blanketing the sand out< I pulled a piece of it back and noticed it has a lot of red worms (I assume they are normal and prbably brissle worms and also various other critters and pods.