what are its symptoms? loosing arms, melting etc?
water parameters?
have you dosed the tank with anything...fish meds
need some data to diagnose the problem..
no tank dosing. I do regular water changes. The star is not moving and its extensions are shrinking. I don't have a test kit for reef tanks. Just the regular kit. Last time I tested it was showing high levels of ph. I have changing the water more often since that test. I.mnot sure it is alive now.
If it's melting away, it's probably starving and it sounds like it is already beyond help.
If you're going to keep starfish, which are sensitive to even subtle changes, I really do suggest a reef master kit.