When I setup my new to me tank I had put my rocks in before filling the tank up. I was trying to keep my rocks wet and worried about losing the bacteria. Well that caused a lot of crude and sediment to settle in the holes of the rocks. Can I take my rocks out and shake them in a tub with water during a water change? I used a power head and a sort of hosed off the rock to see what it would do and a lot of stuff came out the rock. Clouded the water up, but then everything more or less settled back down onto the rocks and sand.