Chemi Clean is a great product, but I wouldn't use it weekly.
It does negativly affect the biological filter in your tank to some extent. However other than that if the directions are followed and the 30% water change is done after the treatment I have never lost anything by using it.
I have clams, shrimp, SPS, LPS, fish all were fine. Anything like this always has a risk, but there have been two cases in the last 4 years where I deamed it worth the risk to cyno outbreak to try and everything was ok.
Check your phosphates and make sure you have good water flow and this will help remove the phosphates problem.
Thanks
Brandon