I have a 55g planted tank. It has been established for over 3 years. I have not added anything new in plants, fish, decorations, or equipment for well over a year. I have 2 discus, rummy nose tetras, a pleco and several assorted algae eaters. About ten days ago all of my grass like plants (I could look up their names but it is all the tall skinny bladed plants) started to look bad and began to have a brownish slimy sediment on them. They quickly faded to oblivion. The broadleaf plants seem unaffected. After about three days of this the water started to turn brownish as if I had stirred up sediment. within a few more days the entire tank was totally brownish - maybe alittle white-ish murky, as if you had put a gallon of mud in a five gallon bucket and stirred it all up. Visibility is about one inch. The fish seem unaffected, although for a bit the rummey nose teteras did not have a rummey nose. Everything seems to be coated in a layer of sediment. For the entire three years I have done a weekly 80% water change (aged primed) so all water parameters have been 0% for years, nitarates 5% and I have never had any such problems. I have the lights on 6 hours per day. Assuming this was an algae bloom I did a three day blackout - no difference. I wash all filtration equipment in aquarium water not tap water. I have now changed 80% of the water about 8 times out of ten days. Still VERY murky. I have read about bacterial blooms but the conditions don't seem to apply. I am at my wit's end and don't want to pull the trigger on creating a "hospital tank" for the fish (screw the plants) and cycle another tank for months. This is an office tank so I cannot cordon off a disaster zone if you know what I mean. Any advice is very welcome!