Welcome to RS!
I just hunted this thread down because i saw in your other post about the clam. The tanks been running for a year now and thats what i wanted to know. fix your alk issue and try again if the clam dies.
Sometimes these things happen and no one knows why. Its a risk we all take getting live stock. If i was you with that kind of lighting i would go for an easier clam like a light loving Gigas! You have the room for it
