Update:
I'm into my second water change with ESV B-Ionic. In total I've changed out around 90 gallons of my 165 gallon total system volume over 4 weeks. The Urchin spawned again when the new water was introudced.
Nitrates are reading 4 PPM.
Salinity around 34 PPT
Phosphates are around 0.04 PPM
Ca at 470 PPM
kH at 3.4 meq/l
Mg at 1340 PPM
A little good news - Something spawned on my MP40 and layed a clutch of eggs. I have no idea what these eggs are as I've never seen them in my tank before (I've got lots of snail eggs on the glass and I've seen the Skunk cleaners carrying eggs on their tails before). I'm guessing these are either the clownfish laying eggs or some free floating eggs that got pulled into the powerhead. The clownfish don't usually host on this particular powerhead and no one is currently at the clutch. I'll try to get a pic of it tonight if I can.
The dosing and water changes are keeping the system pretty stable. I'm still dosing 100 ml of 2 part per day.
In all, I think I've lost around $1,500 worth of corals. I still dont know what to attribute this to. If it is a pest - it has to be a pest (or pests) that attack multiple families of SPS (hence why I thought it may have been the vermetid). More likely I wasn't as stable in the system as I needed to be.
I have lost 1 Montipora, all Millipora, most Acroporas, all torts (would these be considered Acro's?). The items that still seem to be growing and thriving are: Montipora Confusa, Rainbow Montis, montipora digitata, bali green slimer and those acropora that came in with the Zanclea Hydroids and the blue squamosa clam and a few of Mike's corals and the vivid purple monster.
I have so many things that I could attribute this to:
4 keyhole limpets were in the display tank - never knew what they were or that they may eat Xooanlthlae
an Infestation of Vermetid Snails that I brought in in february. never knew what they were or that they can irritate SPS to death.
Brought in Aiptasia on my one piece of live rock - knew what they were and tried everything documented to eradicate them:Laser, Kalk Paste, Copperband, Peppermint Shrimp, Aiptasia-X and now on to Bergia. It's everywhere in the sump and the display.
Added a UV Sterilizer to the return plumbing (through a mag 18). That could have changed the parameters of algae growth in the display tank - cuasing the limpets or vermetid or crabs to start going after the acros.
Changed my LED light cycle from 13 hours to 9 hours.
Changed my LED light mix to drop warm and cool white to 15%
Swapped out my sump due to mechanical issues
switched salts (via water changes) so many times: From IORC to RSCP back to IORC to RS Normal to ESV B-ionic.
Using red slime remover for a severe outbreak of cyano
So many floods. two floods since july with one of them affecting the salinity in the tank.
Heck, it could even be the way I feed that's causing this. I turn off all the pumps and skimmers when I feed for five minutes.
Added a Blue Squamosa clam without quarantine
Added all SPS without quarantine