You should do a Walstad/ NPT!!!
Does the tank have a hood? If you have proper lighting you can put in a variety of fast growers like anacharis, hornwort, or wisteria.
Or Duckweed! Floaters are supposed to be great at sucking up nitrates and such.The proof will be when you have to regularly remove handfuls of it to keep it under control. But thats a good thing because it means that your water will be clean. I've been looking for duckweed/ frogbit lately... for invasive weeds they're pretty hard to find