saltwater fish are dying

Question
I set up a saltwater tank in April. I used 3 hermit crabs to get started. Once my levels peaked and dropped off I then tried some fish. All my fish die, usually in 5-7 days sometimes after several weeks. 2 of the crabs still remain and seem to be doing good. I do my 10 water changes each month and filter changes. I use a chlorine remover and slim protector at water changes and when I add new fish. I have had 2 pair of clowns, a tang, an angel and some others and they all die. When I add fish I only add 1 or 2 at a time so I don't overload my bio-filter. I have a 46 gallon bowfront tank and all my levels check-out ok.What else could be happening. I have had marine tanks in the past and had very little trouble, but this recent undertaking is very frustrating and expensive. Please help. Thanks David

Answer
Hi David,
  Did I read correctly? Are you doing 10 water changes a month? If this is indeed what you are doing it would be difficult to keep water conditions stable enough for delicate fish and it would also lead to problems with constant changes, biologically speaking. This may affect your bacteria effectiveness. Please get back to me with all the levels of salinity, PH, ammonia, nitrites, nitrates and temp. I hate to see anyone lose fish, especially someone as conscientious as you are. Get back to ma with your readings ASAP and I will have more info to base my suggestions on. thanks, Gerry.