Astrea snail question/problem????

[Delphinus]

The ammonia reading has got to be a sure suspect. Weird, my theory is that you should never have to test for ammonia, you would know about it anyways if it was there (e.g., something died). Very strange! I'd almost be suspecting your test kit on that one .. knowing your tank, I have a hard time beleiving you could get an ammonia spike.