does anyone vacum the substrate? the reason i ask is my tank has been running for about 5 years and there are some dead spots under the rock where i can see grey matter build up its not really accessible to get at ,wondering if this could have some bearing on the recent apperance of some cyano ?the substrate is aragonite (small type) i do weekly water changes water perimeters are all good ,also should i vacum the accessible places ? or leave it alone?