I haven't the foggiest idea why it crashed out. Was running fun for several months, I was doing my water changes and topping off like a good aquariust should, then everything started to die off. My ph was testing out at about 8.2, no ammonia, no nitrites, and practically no nitrates. I assume my alk was good since my ph was good, I had no test kit for alk. Even the coralllne on the live rock died out. Total mystery to me. I kept the rock, to use for base rock and threw a few pieces of it in the sump to replace most of the bioballs.