Just posted my cyano update, you just need to watch your nutrients closely. I let my nitrates bottom out unbeknownst to me (an old nitrate test kit told me my nitrates were at 10ppm when really they were at 0 for well who knows how long....). As long as you have a lot of plants, the circulation shouldn't need to be very high to keep nitrates away, as long as you have photosynthesis and a lot of plants with the necessary fertilizers and a good balance of them, you should be ok. The plants are pretty good little filters of water and actually create their own currents.....also the light on the top warms the top layer and the cooler water at the bottom will rise to take it's place, it a good way to circulate water as well, as in nature. Anyway, get lots of plants as stated above and keep them fed, you should be ok. You might need to treat the tank no matter what you do, that cyano is a you know what.