When I was first planning to move my 29g marine aquarium (populated with two clowns, a damsel, a pseudochromis and 20-30 lbs of live rock) to another room, I decided to replace the hang-on filter with a canister and change the live sand substrate to crushed coral. That day came on Sunday when the power went out and my filter died, necessitating an immediate replacement. I saved about 1/3 of the water, then completely scrubbed out the tank (no bleach or soap). After placing it in the new location I filled it with well-rinsed crushed gravel, the live rock, the water I saved plus fresh dechlorinated saltwater, installed the new filter, and waited until the water was clear before adding the fish. By Monday morning the fish still looked shell-shocked, and by the evening they were dead.
The standard test-strip didn't show anything out of whack. I want to repopulate the tank, but what else should I look for that could be the cause of their death? I suspect that the worms now crawling on the glass (see photo) aren't the problem as they must have been there all along (think War of the Worlds), so what else chemically should I test for?

The standard test-strip didn't show anything out of whack. I want to repopulate the tank, but what else should I look for that could be the cause of their death? I suspect that the worms now crawling on the glass (see photo) aren't the problem as they must have been there all along (think War of the Worlds), so what else chemically should I test for?
