I have a 600 SW/Reef tank that up until about 3 weeks ago was fine. I had a spike in ph , which I too quickly brought down with co2, and up again to fast with cal. My fish were fine, but all my live rock and inverts died with in about 2 weeks. I've tried adding new snails, crabs, etc. they're ok for a day or two then seem to become paryalized die. all my levels including Iron r ok. any ideas. oh, i've done 4 water changes ( approx 150 gal at a time) still no luck. I really need to get my cleaning crew back, quickly! I have all sorts of icky stuff growing now. My lighting is down to the bear min. Please help!!!