To be honest, your tank is a difficult shape to run as low tech. It is very tall and doesn't have lots of surface area for the number of gallons of water. It certainly is possible to do and many people have done so successfully - but - will be more challenging for you to learn on starting out. So please don't be too discouraged you are having troubles. It can be done! But will take time and effort.
Here is the best quick guide I have found for algae: https://www.advancedplantedtank.com/...h-plllars.html
Because you said you have cyanobacteria, I wonder: Are you providing fertilizers? N, P, K, and micros? Do you have good filtration and water circulation to eliminate ammonia spikes? Are you keeping your substrate and filter clean?
This is the best guide I have found to planted tanks online: https://www.advancedplantedtank.com/...h-plllars.html
The website has tons of great information about both high and low tech tanks. The principles are the same for both types of tank, the only difference is what levels you adjust things to keep the tank in balance.
I don't have any experience with a large tank like a 55 gal. My tanks are 10 gal and 29 gal. But here is how I maintain my tanks to give you some ideas:
Water changes 30-50% every month. More often when the tank needs attention. Less often when I forget.
Automatic fish feeder with flakes. When I remember to feed the fish, I offer something different for variety.
I top off evaporation with RO water. I have hard water and don't want to build up more minerals in the water than necessary.
I add dry fertilizer every time I do a water change. N, P, K and micros.
The tank is heavily planted, with mostly anubias. Also some crypts, vals, ferns, and moss. Anubias grows slowly so I don't need to prune often, and it can handle tank conditions well. Win/win.
I have plants in riparium planters at the water surface. So roots in the water, leaves in the air. This is the same purpose as floating plants, they soak up excess nutrients. I don't like floaters because I don't need them to block my light, so this works better for me. Plus I think they are pretty.
I have lots of cleanup crew. Cherry shrimp, pond snails, MTS snails, one mystery snail. They don't eat much algae, but they do a great job of cleaning up extra food and debris in the tank. This eliminates extra nutrients that would benefit the algae.
I keep sponge on the intake to my filter. Helps keep the filter cleaner, adds more surface for beneficial bacteria. Also a lot easier to clean than the filter. So I clean the filter maybe once per year (just rinse it out, wipe out any buildup). But rinse the sponge in tank water with each water change.
I use a split photoperiod with my lights. 5 hours on - 4 off - 5 on. I had a good balanced tank but still trouble with BBA until I changed to split photoperiod. So 10 hours total of light per day. Generally, for low tech, you want 8-10 hours of light per day. Maybe even less.
Some ideas for you to consider:
You need fertilizer for plants to grow. Are you using any? Yes, fish can provide some nutrients but they rarely provide enough and basically never provide nutrients in the proper balance that plants need.
Here is the best explanation for plant growth that I know of:
Plants need light, nutrients, and carbon (CO2) to grow. There are a whole bunch of different ways to balance these to allow plants to grow. There are better ways to balance these so that plants grow healthy. Usually, when plants are growing healthy, algae isn't much trouble (might still be there but not too much).
The thing with low tech is you are choosing to limit your plants' access to CO2. So that's the thing that will limit the plants growth. You need to make sure the plants have plenty of everything else or they will not be healthy. Depending on the plants, maybe will even die. So make sure you have plenty of fertilizer and plenty of light. You can always dial back the light a little if necessary, or use floating plants.
You may want to add a sponge filter. Maybe even another HOB. Are you getting good water circulation throughout your tank? Does your filter seem to be cleaning the water adequately?
You really don't have much plant mass in your tank. Consider adding more. Floating plants? Stems that grow fast and are easy? Slow growers like java fern, anubias, moss, that are easy but require less maintenance (also harder to diagnose problems though because of the slow growth)?
How many hours of light does your aquarium get? How intense is the light?