Problem -- High dKH and CA

[feel200]

Hi there

My 80 gallon tank's measures are as follow:

dKH: 16 (high?)
CA: 480 (high?)
Ph: 7.9-8.0
No3: 5
PO4: 0-0.025

Problem I have are...
- whenever I place in new corals... 30% will die within the next 2 days... the ones that survivies are doing ok...
- whenever I place new shrimps such as doctor shrimps... 75% will die within the 30min... the ones that survives will die within few days...
- whenever I place a star fish... 50% will die almost immidiately (not moving and then like vomitting some gray stuff out of the mouth)

Is this caused by my high CA and dKH? And they suffer a shock when placed in my acquarium vs the water at the fish shop?

Thanks!

[thegrun]

Yes both your alkalinity and calcium are high. I would suspect you are using a high quality reef salt mix which have higher than normal calcium and alkalinity levels to help supplement reef tanks with a lot of stony corals and/or clams. I would switch to a salt mix lower in calcium and alkalinity and let your levels fall down to 440 calcium, 11 dKH alkalinity. How are you acclimating your new fish? Many stores keep their saltwater at a low salinity level and fish need at least a week to bring the salinity back up to 1.026 from the water they have been kept in. Ideally you should be quarantining your fish for 9 weeks which offers a long time to raise the salinity. There could be other issues with your tank also. Have you tested for copper which will kill invertebrates quickly?