So I'm 24hrs in with the chemiclean treatment and reporting observations.
A little tank history first:
It's a nano that housed a mantis shrimp and clown fish for many years with little maintenance, so the sand bed became a nutrient trap. After the mantis I decided to make it a reef so the sand bed was removed months ago when I couldn't control my NO2 and PO4 and have left it bare bottom since. I only use a filter sock and skimmer to clean my water and started carbon dosing to remove the leaching nutrients from the rocks before the sand bed was removed. I did reach excessively clean levels NO3 undetectable and PO4 at 0.03. I feed excessively a variety of frozen, flake and pellet fish foods as well as several coral foods several times a day and amino supplement in an attempt to raise NO3. No success. When I dial down the carbon dosing I get algae growth and a raise in PO4, not NO3. All corals, except one monti, never lost color and I attribute that to the excess in food added daily. Believe that particular monti was originally placed too high. Growth did slow and I think it's the lack of NO3. I recently started dosing NaNO3 to raise NO3 to 2-3ppm, works like a charm.
I've only really had continual trouble with some zoanthids, not most. We all know the mysteries of these! I've done several different dips for new arrivals and trying to figure out why certain colonies don't open fully, and some not at all. Only ever lost one colony. The dips usually provide temporary results. The dips I've done: iodine, furan2, peroxide, revive, flatworm exit and more recently bayer for the new arrivals. Through all of this I know for a fact that there's no parasites in the tank lol. I've even found some luck with physically scraping the polyps surface with some of my metal frag tools (not recommended to most people BTW). Most of them get better over time with repeated dipping and cleaning but it's exhaustive and I don't have the time anymore for individual treatments of >50 frags with more coming soon from friends.
Treatment:
Anyway, I left my filter sock in even though it's about time to change it. I usually change it only when it overflows because I don't have many fish and the lack of a sand bed.
I left my skimmer running but pulled the collection cup off because most of the crashes I found spoke of oxygen deprivation. My skimmer started going nuts within seconds and my tank is loaded with microbubbles nonstop.
I also read about bleaching corals, especially sps. It's been attributed to drastically cleaner and clearer water so I lowered the light (Kessil A360) intensity from 60% to 40%, but kept the spectrum. I don't know how much of a factor this would be for me because it's very low nutrient to begin with but better safe than sorry.
My Apex did show that my pH dropped to 7.52 last night which is lower than usual but the box does state that O2 and pH could be affected.
All my fish, inverts and corals are doing fine.
Most of my Z&Ps are open a little more than lately. There's a couple that haven't been open for about a week and I spotted them open for a short period today when I got home.
My sps all look good. My montis, birdsnest, millepora, and birds of paradise have full polyp extension but that's nothing new. My acros have better polyp extension this evening

I also see the usual pods running around the glass.
But best of all is most of the algae (at least three different kinds) is turning brown. This has mostly been growing on the (many) newer frag plugs and part of the birdsnest that has been dead. I know that the place I get most of my frags runs much higher NO3 and PO4, so it's just leaching out in theory.
Thoughts:
The box states it's an oxidizer so it shouldn't kill regular bacteria much as they have a natural defense to that. The reaction that I'm seeing with the algae is exactly like when I've done peroxide dips in the past. This makes complete sense because peroxide is an oxidizer also. So in a sense this is just like when people dose their entire tank with peroxide. This just might be a little safer for some people since there's an established dosage to follow. It also explains the pH drop but I won't get into the chemistry here.
I've already prepared for the 20% water change at ~48hrs per instructions.
Sorry for the length but I believe more info is better when researching something for your beloved reef! Hope this helps anybody thinking about it.