Cyanobacteria: Newbie Fail

[Bumblebeeatrice]

I'll preface by saying my tank is a 5 gallon tank about 2 months new. It's been populated by a few ghost shrimp and a nerite snail. I'll also add that I am incredibly new to this, and don't yet have have a lot of the experience, money, or consistency required for this hobby. You'll see all of this in action momentarily. I apologize in advance for the long read, but figured the more info I include, the easier it will be to diagnose my problems.

For the first month of my tank's cycled life, the NO3 tested consistently at 0ppm. I recently started a regiment of liquid nitrate/fertilizer supplementation. I have a goal of 10ppmNO3, but I haven't perfected my dosing schedule yet.

I'm also poor and, as a college student, have almost no sleep schedule to speak of. The lighting period on the tank ranges from 8-15 hours per day, depending on when I am home to turn the lamp on/off. Currently the tank sits below a 4w LED desk lamp. A few of my plants have high lighting requirements so I tried to make up for lack of intensity by increasing the photoperiod. This did make the plants a little happier, but from my vague understanding of CO2, the levels probably fluctuate a lot more than they need to. I do not run a CO2 system, but I dose the tank with API's liquid CO2 before I turn the lights on in the morning.

I also set up the tank without considering waterflow. I had a sponge filter set up behind a piece of driftwood in an alcove behind sloped substrate. It looked awesome, aesthetically, but the only real water circulation was happening in that one back corner. The kitty corner of the tank had almost no water flow, as did the portion in front of the driftwood. All of those portions are part of an unplanted sand path, as well, which means they received uninhibited exposure to my lamp light.

So what happens when inconsistent CO2, a long photoperiod, poor water circulation, and low nitrates all happen at once? Apparently cyanobacteria! Luckily I noticed it before it overtook anything. I had 3 spots of my sand about 1 square inch each and a baby plant growing a lovely blue-green slime. Gross.

I overhauled my filter system and improved the water flow, vacuumed/peeled up as much of the CB as I could, removed the plant, blacked out the tank for a few days, and turned off the heater. As soon as I turned the lights on again, though, the CB came back in all its slimy glory. After a week of fighting, I went a little nuclear. Removed the filter/sponge, squirted some H2O2 directly on the affected areas, waited 12 hours, vacuumed up the newly-dead slime, and put the filter back in. So far, it seems to have worked like a charm. No new ammonia after 24 hours, either, so I don't think I killed my biofilter with the H2O2. Score.

If you've read this far, thanks for sticking with me. I've researched as much as I can on my own, but think it's time for advice from the experts. Here are my questions.
1: What level of NO2 should I aim for in my aquarium? I don't ever want to exceed 20ppm because I want to keep a neocaridina colony in there once I stabilize everything, but I also don't know if keeping it at/below 10ppm is asking for another cyanobacteria bloom.
2: How can I improve water circulation in such a small tank? I've read that I'm looking for a flow rate of about 20gph, but all the pumps and powerheads I've looked into run in the 90+ range. I'm hesitant to buy a bulky submersible filter or a HOB filter because my tank is so small, but I'm considering that option if my ratchet pump solution fails.
3: Should I still dose my liquid CO2 every morning? Could that be a contributing factor to cyanobacteria?
4: Should I aim for longer photoperiods of my low intensity light, or should I try to keep it shorter?

Thanks in advance for anything you have to say. Feel free to roast me and my inexperience, too. The extra shame might help me get my crap together.

 

[Aiken Drum]

I think you are overcomplicating this way too much.

Are you planning keeping fish in this aquarium or is it going to be just an underwater garden with a few shrimp and snails?

If you want to keep fish then i would get fish in there before starting to dose fertilisers. Fish and the nitrogen cycle will get your nitrate up. See how things are going with fish before starting an excessive dosing regime.

Your light is on way too much. 6 to 8 hours of a desk light is sufficient for growing low light demanding plants. If you cant inject CO2 and provide high level lighting i would remove the high light demand plants. Just increasing the lighting period isnt a good substitute and will just encourage algae. Liquid CO2 isnt a good substitute for injected CO2 either. It may help with low demand plants but not the ones that actually need the CO2.

Simplify things down.

 

[Aiken Drum]

Plant growth and algae control is about balancing nutrients, light and CO2.

You are trying to grow high demand plants and cant provide this balance for them. Try to compensate and throw a light on for an excessive amount of time and algae or cyanobacteria will proliferate.

 

[Bumblebeeatrice]

I think you are overcomplicating this way too much.

I've been known to do that

Are you planning keeping fish in this aquarium or is it going to be just an underwater garden with a few shrimp and snails?

I'm not planning on keeping fish in there. Just a shrimp colony and the nerite. Its only 12x12x9 so there's not really enough swim space to support a nano school.

Your light is on way too much. 6 to 8 hours of a desk light is sufficient for growing low light demanding plants. If you cant inject CO2 and provide high level lighting i would remove the high light demand plants. Just increasing the lighting period isnt a good substitute and will just encourage algae. Liquid CO2 isnt a good substitute for injected CO2 either. It may help with low demand plants but not the ones that actually need the CO2.

Simplify things down.

I'll definitely decrease the light duration then.

I'm considering a rescape in the next couple weeks. I do love the way the s. repens and a. reineckii (the more demanding plants, I guess classified as med-high light) have taken off in my 10 gallon. They grow slowly, but the color is awesome and i have no algae problems. I don't run Co2 in that one either. I think the balance is better because the 10 gallon is stocked to the max and the No3 chills at around 30. The light is also about 2wpg in the 10 as opposed to the <1wpg in the 5.

A huge reason I started my 5 gallon was so I could really learn about how to keep a low tech tank. Weirdly enough, I like that it's complicated. I get a lot of joy from the experimentation. The cyanobacteria was gross, sure, but it was fun learning about all the factors that contributed to its growth as well as troubleshooting the tank setup to prevent another bloom. I'm hopefully getting a better light (with a timer!) this Xmas, which will help the plants photosynthesize better. I don't want to just give up on the plants I have

I'm slowly working my way through Walstad's book and am considering using capped and mineralized soil as the substrate. As far as I can tell, that will help bump up the nutrient and Co2 level without adding fish or an injector. Am I thinking right?