We all have our own mad scientist methods, what works for me others would probably find archaic. My hands are in my 20 gallon every 3 days, doing a water change, scrubbing the back wall clean, using a tooth brush to clean corners, scrub rocks off and a turkey baster to blast the detritus from the rocks. I am obsessive I will admit but for me the results are worth it. This is the reason why I like nanos, maintenance is so much easier at a much lower cost. No skimmer, minimal charcoal use, water changes, water changes, water changes...Never test for N/P, all that ever did was make me a nervous wreak.
It's the kiss method and I strayed from it the last two years, the results were disappointing. The nano below had no skimmer, no GFO, just water changes. Point is I feel almost any problem with a nano can be improved with routine water changes, ya just do not need all the bells and whistles.
Now you have a noticeable trait of attention to detail (which is excellent) and probably enjoy the engineering.
The only times my tanks have gotten dino was from dosing amino acids, never failed.
I am willing to bet if you put a T5 fixture on that tank you would see a reduction in the occurance of cyano. Have you tried Microbacter7 at all?
Now I will take my crazy methodology and find the door. ;Bookworm