05-04-2013, 01:46 PM
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I can't see the sand clear enough to differentiate, but this is either basic algae or cyanobacteria. I'll assume basic green algae; cyanobacteria is like a slimy film.
Light is the cause of the algae, and it does seem to be bright, and the place you mention is right out in the open, so that coincides. If this is the 50g tank in your Log, two T8 tubes will not be overkill but it will have to be controlled, as you've seen by reducing the photoperiod. And more floating plants will help. The plants look real in the photo, though in the Log is says they are fake...?
Bear in mind too that the white sand substrate is going to increase the internal light as well. More chunks of wood or rock to cover some of the substrate would also be good.
I would not add iron. This is notorious for encouraging algae. Flourish Comprehensive Supplement contains all necessary nutrients, and in proportion to each other which is very important for plants. Once a week should be sufficient, just stop using iron.