So quick update is. Ritchie came and tested all my water and found a low KH so something I need to rectify. Also a small trace of chlorine/chloramines. I think these are coming in from my mains tap as my drum cleaning comes directly off that but also need to test from my purifiers to make sure. He also found a couple of skin flukes so I am treating for those and for gill flukes as a precaution. Hopefully this will stop my problems and I can get back to a happy, healthy pond Thanks for your help and for Ritchie's number. Really helpful and knowledgeable fella and would recommend him to anyone having problems.

Thanks again

Craig