http://forum.aqua-fish.net/ A forum devoted to aquarium fish, plants, techniques and fish keeping as a whole. en http://forum.aqua-fish.net/?topic=if-someone-could-respond-plz-#1 i have a 12inc. oscar in a 90 gl. tank the water is cloudy ive tested it everythings fine i do a water change every week still hasn't cleared any i got a power head pump running to a biofilter still nothing i was wondering if i could do a complete water change with out hurting the fish cause i want to put sand down instead of gravel? sk843326 2010-10-10 http://forum.aqua-fish.net/?topic=if-someone-could-respond-plz-#2 100 % water changes are not ideal for the fish, a lot of the bacteria will be removed as well. You can still change the substrate without removing all of the water it just takes a bit of time. Do you use a gravel vacuum on a regular basis as it could be dirty underneath. mickey 2010-10-11 http://forum.aqua-fish.net/?topic=if-someone-could-respond-plz-#3 Try vacuuming out your substrate, sometimes waste remains trapped in the substrate and when it is disturbed it is shot into the water making the water cloudy and stinky. StewPadasle 2011-06-27