I'm a newbie too but I'm in the same boat so I'm just leaving a comment to bump this post so hopefully I can learn too.
I ended up buying a timer and have it running 5 hrs on, 4 off, and 5 on every day. I also took the sponge filter out and replaced it with an 80gph fountain filter. The tank is so small, though, that even that baby pump. overwhelms it with flow! I ended up stuffing it with a sponge to decrease the flow and attaching a little acrylic spout so it spits the water out above the waterline. It seems to stay pretty oxygenated, and my parameters seem alright still (the sponge i stuffed in came from my old cycled filter).I'll second getting a cheap timer so your photo period is consistent. Sounds like you are going for a low tech planted shrimp tank? As long as you do weekly water changes 50%, I wouldn't worry too much about your nitrates. They likely aren't directly causing the cyanobacteria and many folks with planted tanks keep them a little higher on purpose. Adding phosphate or oxygen to the tank will both hinder/prevent the future development of cyanobacteria (as will the liquid CO2/Excel/Glutaraldehyde).
Sounds like you're running a sponge filter, so the water should be fairly well oxygenated. If you want more flow, see if you can run your sponge filter using a jet-lifter from swiss tropicals:
Jetlifter & Cubelifter Shop - SWISSTROPICALSThe Jetlifter and Cubelifter are super-efficient air-driven lift tubes that power our Cubefilters, Tower Block Filters, Mattenfilters & Cornerfilters.www.swisstropicals.com
They actually move a lot more water around the tank than the standard vertical bubble tube most sponge filters have. If it won't fit your current filter, you can just suction cup the jetlifter in the tank to move water around. Or just buy a small sponge filter from swiss tropicals and run it in parallel with your existing filter for a month if you don't want extra stuff in your tank all the time and don't want to fiddle with matting up filter parts.
I grabbed a timer and updated my filter for more flow. I have a new light, too, with a 20 watt led bulb for it. I haven't set it up yet because I think im going to do a full re-scape to fix unrelated problems in my substrate... but the timer worked like magic! I think I can confidently say the cyanobacteria has been vanquished. I think I learned a couple important lessons and hopefully my next try will work out better.Get a cheap timer from the hardware store or grocery store and plug your light into it. Set for 7 hours. You can get a higher watt LED bulb too like 20watts or something. The liquid carbon help kills algae too. Some people have magic water and you might not need to add liquid carbon.