I have had a 240 litre fish tank for 7 months and not had a problem until a couple of days ago l did a 25%water change which l do fortnightly and its usually crystal clear with a day but it didn't clear it was milky so l did a 75% water change but it didn't clear up so l thought it may be the filter..l bought a new one and added media and sponge from the new one and have them side by side..it is getting worse it is milky and greenish now..l googled and it said it could be a bacteria bloom and was suggested to add activated carbon l have done that.mit hasent cleared as yet..l don't know whether to remove my fish and put them in my 55 litre until the problem is solved but obviously worried about overcrowding..l have 5 angelfish 3 gorami.1 rainbow l filament barb 1 molly l cichlids and a few danios..l don't know what to do to sort the problem out