ARSchwartz

If my tank wasn't still covered in the original problem, I would be more inclined to believe that.

Then again, at this point it is completely irrelevant what happened.

Appreciate all the responses, but after running chemi-clean the entire tank crashed within 24-36 hours from dosing. Followed instructions precisely, yet it failed and epicly.

Performed the 20% water change anyway, though all fish (even my cleaner shrimp) are dead. Heading out of town so will let it do its thing and see if it looks any better/worse when I return in 2 days.

Substrate ~2yrs old. Crushed coral was put in when I moved to Austin and the old sand was recommended to be discarded as it was ~3 years old at that point and would be pretty disturbed during transit.

This problem is very new, the most recent change to the tank was the new light fixture I purchased, which was a 48" Coralife Lunar Aqualight T5 Lamp High Output Fixture. This was done less than a year ago, so bulbs are still plenty good. I'm currently running lights for 10 hours a day, darkness the other 14.

Creeping back is an understatement, tank looked good for a matter of days, within a month it's about at a complete takeover again.

For what it's worth, this is the protein skimmer I've always used: http://www.marinedepot.com/ps_ViewItem.aspx?idProduct=AC3123&child=ACRPDB