not sure if water hyacinth is legal over where u r, but if it is legal I'd go out and get some asap. Also , there are plenty of plants that should do well in the dt with rays, just aren't rooted. Water wisteria is a stem plant that does better rooted, but can grow floating, get some form of water weed that will grow like crazy. If you have enough plants in there your nitrate will completly dissapear. I dose 10 ppm of nitrate in my ten gallon every other day and I have trouble getting a reading at the end of the night. If I were you I would start looking into building an algae turf scrubber as well. I'm making my first one tommorrow so I've never had any personal experience with any pro's or cons, but I think it would be worth a shot. If not I'd look into making a refugium at least.