nice preservation of all the animal life and corals, really shows the benefit of your sticking through the tough challenges on this unique tank
the key to managing that kind of growth, whatever it may be, is not letting it spread. algae cannot spread surface to surface if it is removed/burnt however we want to slice it. only allowance lets it build up, although nobody wants to work day by day on keeping it at bay either we have to find a balance.
Its ideal to beat this algae before you start over. the exact same leadup will occur and in a larger tank, even more reason to not access it/it will take over each surface. I feel its only right to move on when this one is beaten and sustained.
You should lower the light intensity by about half, corals will tolerate that fine for what you have in there and how small the tank is/closeness of light and the invader is used to high production lighting in a system with fish bioloading (algae fuel) and allowance to take over. that's the formula for takeover whether its bryopsis or gha or invasive macro etc.
if you want to restart the tank you can, but you'll be missing out on learning critical control factors for invasions that your region selects for, Id work on this until it can be controlled. Most will not do that, they're determined to start fresh/understood but the tendency is to do the exact same arrangement only with clean rocks, and the arrangement and timing of things has a place in this takeover invasion.
for example, adding fish too soon/algae fuel is a common starting point. I only add fish/recommend add fish when the system is running algae free and nearly totally stocked with coral. this tank here is opposite/open space, high light, fish bioload and feed, plus an adapted invader with allowed real estate.
This tank or a new tank / since you are at give up level/ should be taken back to step one. remove the fish/sell him/hold him at the lfs which ever it takes but even in your new tank, fish too soon means repeat.
I would remove fish, and use the test rock method to discern what works for the algae. There are several ways of applying peroxide or fluconazole and many fixes, but that begins the process of $ buying things without pre modeling anything, total guesswork can be equally frustrating.
There are two types of system invasions: rampant ones where a full tank shot shows the invasion fully, and full tank shots where the tank is totally pristine free of invasion but the keeper is wanting to reduce the workload associated with keeping the tank clean. Its better to never let the algae take over, never stop cleaning and killing it/ if we stop and let it take over then all the mechanisms that work to suppress algae are stopped as well and in a larger tank it will be 3x harder to control overall.
You wouldn't want to add fish to a nano system until algae-excluding corals and coralline are all in place and working well, to me that's a critical changeup for this tank or for the new tank.
the test rock method has to be pictured here in steps so we can see if it was applied, rasping and scraping is the most important part, then the final application of peroxide outside of the tank. This action has to result in an algae-free system, we don't have that photograph above after the peroxide discussion in November in order to track growback.
starting with the algae free rasped rock, where a metal knife scrape renders the whole rock clean (and the tank is disassembly cleaned to remove algae off the glass etc) and peroxide added only to the cleaned portions lets us see how fast the growback will be over time and updated pics.
if you are determined to start over before fixing this invasion, I would buy only real reef rock from a pet store in a tank at the store. I wouldn't buy dry rock or other kinds shipped to you, that way you know the history of the rock when you buy it. pay extra for this rock. Don't add fish until you have completed coral stocking and demonstrated several months of growth in the way you want the tank to run. at no time can algae be permitted to grow on the new setup...then add fish and all the mechanisms designed to support them, this will help your next venture by being opposite in arrangement and execution
your tank went through unique challenges where it had to sit for weeks and weeks, although tough the fact this amounted to plant growth isn't surprising, its part of the dynamics your system is expressing over time
