I have a 55 gal tank with loads of Texas Holey Rock. I have rigged two long shafted plastic tubes to routinely siphon the superficial waste, one with a curved tip another straight. NH4, NH3, NH2 not a problem. How often should I completely break it down, removing the rocks and clean the entire tank? The Rock initially was snow white but naturally has stained but still looks pretty neat. I know there is probably debris lodged under the rock but minimal that I can see with the white sand.