So I am about to blow a fuse. I have done everything I possibly know how to do. I will try to give you guys as much information as possible and then I hope you can help me with my problem.
I have recently set up an aquarium. It is 55 gallons and has been set up for about 3 or 4 months. I have had the brown algae growing on the tank for a while now. I have just been scrubbing it off. I know it came on the plants I bought because I work at the place I bought them. I have Flourite substrate mixed with Super Naturals Black Tahitian Sand. I do 50% water changes every week and after my water changes I put 5 mL of Flourish and 5mL of Flourish Iron as well as a run of the mill dechlorinator and A.C.T benefitical bacteria. I just recently put carbon and zeolite back into my marineland filter (for 50 gallon tanks *I know I need a bigger filtration system, Im poor though ><"*) as well as filter floss. I scrub down the patches of brown algae every day. I even let it grow on one side, it doesn't form dark patches but an even coat of brown. I have Hagans CO2 injector but with a ceramic and hand blown glass diffusor. I have a wide range of plants. A few types of (Corkscrew, Italian and Jungle) Vallisenaria, 2 types of (Red and Green) Cambomba, Wysteria, Moss Balls, Dwarf Hairgrass, Giant Hairgrass, Water Sprite, Anacharis, Onion Plant, Moneywort, Microswords, Java Fern, Wendetii of some kind of variation, and a Amazon Ruffle. I have invested so much into this tank. And now this brown stuff is growing on the plants... I cant clean them, they are too delicate. I have 12 hours of light on the tank a day, its on a timer. It gets no sun light and isnt by a window. I cant tell you how much CO2 is getting pumped into the tank cause I honestly cant figure out how to count it. I have Ghost Shrimp, 4 baby Black Mollies, Banjo Cat (never to be seen), 2 Clown Loaches, 5 Fancy Guppies and 1 feeder Guppy, 1 albino coradora cat, 1 tadpole (I just put the other one outdside because he turned into a frog), 1 glass catfish and 1 male Betta fish... I have a shoplight about 12 inches above an open topped aquarium with 2 fluoresent bulbs. Ultra Sun by Zoo Med. CRI rating of 98 and 6500k full spectrum lighting. Its 32 watts each. I also put 1 pack of Flourish tabs in the substrate about 2 months ago. My water stats are: Nitrates:.25ppm Nitrites:0ppm pH: 7.8 Ammonia: 0ppm Copper: .00ppm I do not have a test for phosphates or water hardness yet. I assume it is hard water because its Florida... and the water is always hard. I have tried cleaning it throughly, I gravel vac every week as good as I can although there is always some amount of organic disolving matter in there at any given point in time. I replace the floss about once a week when it starts to get dirty and I feed the fish about 2 times a week, and Im talking about a small small pinch. People over feed their fish... I do have the option of moving the fish into a smaller tank if need be. I hate this brown stuff, I am thinking its diatoms but what do I know! Please I need some help. I work at a pet store and no one has any idea on how to rid me of this ever occuring problem.

Thank you and if you have an questions feel free to contact me!