I know you have all probably read this over and over again but I really need help; I have a 18g tank and out of the blue about a month ago it just went cloudy, when the light is on you can almost see a milk like substance flowing through it. So I spoke to my LFS and he said leave it don't do anything it will sort out. But now some people are saying I should do a water change every day. I did used to do a 20% water change weekly but the LFS told me i was wrong? I have run out of ideas I have a juwel rekord 80 which has a four stage sponge filtration system. PLEASE PLEASE HELP ME! 
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If i remember rightly, I tried that water polishing white cotton stuff, being careful to squeeze it out in old water first as it can be dusty. Carried on with normal water changing and eventually it dissappeared as mysteriously as it arrived. My water has been crystal ever since......shouldn't have said that 
