Cosmoknight74 said:I use Penguin filters (330 and 350) on a 55 gallon with sand and haven't had a problem yet. I removed the extension tube so there is only about 6 inches of tube. The extension tube (I thought) stuck down too far close to the sand. I would leave about 3 inches or more if you can between the sand and the intake.
Right now I have Eco-Complete Cichlid sand mixed with black sand (40#'s eco and 15#s of black). The eco was too white for me, as I was going for a dark look.
I have mixed black sand with play sand in a 10 gallon tank. Didn't really like it. I put in the play sand then the black sand and hand mixed it, so your way may be better.
The sand will work it's way down under the rock/gravel. I have some black lava rock in my tank, and I have left some gravel in the tanka nd put sand over it. Some of the gravel showed in a couple fo weeks. It was red gravel that turned light red (almost pink). I was never happy with that look, the wife picked it out since I talked her into the fish tank. Now I run the show (don't tell her that :lol: ).