Time for an update: the tank is Dino-mite!
As in, currently going through a case of dinos. (No idea what kind as I haven't bothered to get a microscope.) Not a major one though. And the sudden nutrient imbalance that triggered it is gradually being corrected.
What really gets my goat is that was caused by a couple of bonehead moves on my part just when the initial 'new tank' hair algae burst burned itself out and the tank was looking good.
The cause was two-fold:
1. I got several colonies of coral a few weeks ago. The air-freight flights were horribly delayed and it was HOT. The extra 12 hours of delay didn't bode well for some of the acro colonies. A couple were DOA and a few more were quite stressed. Despite my best efforts, two lost their flesh within minutes of being in the DT water flow. Two more lost their flesh by the next morning.
2. Because of the delay the stressed condition I tried to get them out of the shipping bags, dipped and into the DT as quick as possible. I thought I had given them enough time in a large enough volume of post-dip rinse water to remove all of the Bayer dip residue from the colonies. I was wrong. After putting the first 3 into the tank I saw a paralized sexy shrimp go drifting by. Gave the rest more time and 'swishing' in the rinse tub but the damage was already done. A little bit of Bayer apparently did get into the DT.
Result: between the bit of Bayer that got into the DT and all the dead flesh from the 4 colonies that disintigrated in the DT, phosphates shot off the chart. >1 ppm of PO4. My test kit chart tops out a 1ppm but I'm sure it was higher.
The biofilter handled the NO3 just fine. Too fine in fact. Never got higher than about 3 ppm and was back down to 1 ppm within a day.
Only took about 2 days of such a severe imbalance for a good thick mat of cyano and dinos to cover the sand. Burgundy, teals, and green matts ... and green-brown snot strings. Quite the mix.
If I were smart, I would've had a rubber maid tub DT water, a powerhead, and a heater ready to go to put the new corals in. I don't have room for an actual frag tank, but that would've at least let me monitor and nurse the corals for a 2-3 days before putting them in the DT.
Aside from the colonies that didn't survive the trauma of delayed summertime shipping, I lost 2 skunk cleaner shrimp and 3 out of 4 sexy shrimp due to the bit of Bayer residue that made it into the DT. All the fish and other inverts are fine.
Lesson learned.
Now that PO4 is back below 0.05 ppm, I'm slowly dosing nitrate to get NO3 up to ~3ppm to try and re-establish a bit of nutrient balance in the hope it will eliminate the remaining dinos.
Also added my second batch of fish a couple days ago per my original stocking plan. The added bio-load should also help to maintain a slightly detectable bit of NO3.
Previous FTS from May 31:
Tank shots from today: