Mysterious Fish Death
I have a 37 gallon reef tank with about 80 pounds of live rock with some corals. It's been established for about five years. About five days ago I found my cleaner shrimp dead on the bottom of the tank. I pulled him and did a four gallon water change. The next day three PJ Cardinals died, two of which were at least two years old. I did another four gallon water change. We then lost our starry blenny and now our two clowns. The corals seem to be dying too. Hermit crabs are dying. I haven't done anything new in three weeks when I introduced the blenny and some crabs. The only things left seem to be a sandsifting starfish and some snails. I noticed a bright green, almost neon, algae had formed on the sand. That's the only thing new. I ordered a testing kit, but haven't received it yet.
Does anyone have any idea what could have happened?