Thanks for all your thoughts everyone! I'll keep up with the Excel spot treatments for now and try the H2O2 if it doesn't clear up. I'll cut back on ferts too. I do a roughly 30% water change every week and only dose the Flourish after that. I'll cut back to half a dose and see how it goes.
I have been offering blanched veggies at least once a week (mostly lettuces and spinach, since that's what's usually in my fridge), but I never saw the otos eat it- the platies are the only ones who seem to like it. I'll try some zucchini this time around.
One last question: Even before the algae situation, the stem plants have a tendency to grow pretty leggy. I know in my garden outside, when the plants grow leggy they aren't getting the sun they need. I was toying with the idea of throwing an extra 13 watt 65k cfl bulb I have lying around on the tank to see if a bit more light might help things out. I'm fine with continuing excel should the light require it, but I'm not interested in injecting CO2 at this time. Good idea? Or asking for trouble?