Another unfun update for 6/18/20:
What I'd thought was cyano, turned out to be dinoflagellates. My wife's coworker gave me a microscope, I took a peek at the brown gunk, and...(expletive deleted).
The bad news: that's definitely dinos.
The good news: they haven't been killing anything, even as gross as the tank has looked.
So, given the rabbit hole of dino treatments: what will I do?
First step (aside from asking for input here): figure out exactly what I'm dealing with. 'Dinoflagellates' is an imprecise term that refers to a number of different species, each of which has unique characteristics. I found a nifty little PDF to help identify what type of dinos you may run into, and I've attached it here. (Note: I also have a microscope available to loan to the club; check out my thread on that if you want to borrow it.)
I initially thought I had amphidinium dinos. After more thorough analysis, I'm more convinced that I have Prorocentrum dinos. While this sucks, because they can be a toxic species, it *does* mean they go into the water column at night—meaning a UV sterilizer should have an effect.
Second step: nutrients. Thanks to fighting what I thought was a cyano bloom, I was aware that my phosphates and nitrates had been undetectable for some time. I've been feeding heavier for the past few days to counteract this and, while I've seen an uptick in phosphates (0.07 ppm as of my last measurement), my nitrates haven't budged. Given this, I've opted to dose nitrates until they reach a detectable level (and to dose to maintain them). Consensus seems to be that no phosphate or nitrate predisposes tanks to a dino bloom; my money on the 'why' is that dinos are more effective at out-competing other organisms with limiting nutrients.
Third step: competition. I started with dry rock, bagged live sand, and bottle bacteria. I've added frags from other people's tanks, but I'm willing to bet that my biodiversity is still woefully inadequate. Dinos are a monoculture, and they've outcompeted everything else, so my goal is to knock them back while giving other things a chance to scavenge for nutrients before the little bastards can get to them.
@ofzakaria was kind enough to offer me a piece of live rock for my tank, so I'll be further seeding my tank with all those goodies in the hopes it'll provide further competition for the dinos.
Fourth step: UV sterilizer. Hello, old friend; I've missed you from cell culture experiments in the lab. Since I ID'd my dinos as entering the water column, a UV sterilizer sounds like an excellent tool to help kill these (and other parasites) off.
@bfirecat was kind enough to offer me his as a loaner, but I like the peace of mind I'll have in the future, so I snagged one from Neptune.
Fifth step: 3-day blackout. Prorocentrum seem to enter the water column only after a blackout. Bacterial competitors don't need to photosynthesize. Bye-bye pretty reef tank for a few days.
Sixth step: activated carbon. Dinos often have toxins. The point of all this is to kill the dinos. Dying things release toxins. Toxins kill non-dinothings. I do not wish non-dino things to be killed, so I am running more carbon.
Seventh step: manual removal. There was brown crap all over the sand, and some (what I think might *actually* be cyano) on the rocks. I blew off all the rocks with a turkey baster, siphoned all the brown gunk I could off the sand, and just removed as much as I could from the tank to make the rest of the steps more effective.
Edit, 6/19/20: In the interest of more complete data, I'm also noting that I'm still running my skimmer as normal. My rationale for this is that it will help remove dead/dying dinos, and any incidental loss of bacteria is made up for by the fact I'm dosing more every day.
Wish me luck!