Hello,
This is my first time visiting the reef central boards, so please take it easy on me.
I have 2 tanks set up, a 150g and a 75g. Considering both tanks I have a total of approximately 15 - 20 zoo colonies. When first purchased, these zoo's were magnificent, and would open fully each and every day for the first 2 to 3 months they were in their respective tanks. After that period of time, most all of them begin to decline drastically. Not only by how many of the individual zoo's would open, but in many cases the zoo's would slowly begin to disappear.
On some of the polyps I have noticed what appears to be some sort of white substance, almost "chalky", on the shaft of the polyps. Most all of the polyps that have this condition no longer open at all. Many of the other colony's polyps have disappeared to the point that colonies that once contained 100+ polyps are now reduced to maybe a dozen....or even less in some cases.
I have had lengthy discussions regarding this topic with the folks at my local fish store, with little success. I am aware of a type of nudibranch that may potentially feed on zoo's, and I've done my best to eradicate these pests, although a few of them may still linger in the tanks. I have recently noticed a type of starfish, perhaps a microstar, that is often seen attached to the shaft of the polyps. I have included a picture of the starfish in question below. The specimen is roughly 3/4" in diameter.
Is this starfish a possible cause of my problem? Is it the nudibranchs? Is it something else entirely? I have successfully maintained various types of soft and hard corals, with the zoo's as my only significant problem area. I would be forever indebted to anyone who can shed some much needed light on this frustrating subject.
This is my first time visiting the reef central boards, so please take it easy on me.

I have 2 tanks set up, a 150g and a 75g. Considering both tanks I have a total of approximately 15 - 20 zoo colonies. When first purchased, these zoo's were magnificent, and would open fully each and every day for the first 2 to 3 months they were in their respective tanks. After that period of time, most all of them begin to decline drastically. Not only by how many of the individual zoo's would open, but in many cases the zoo's would slowly begin to disappear.
On some of the polyps I have noticed what appears to be some sort of white substance, almost "chalky", on the shaft of the polyps. Most all of the polyps that have this condition no longer open at all. Many of the other colony's polyps have disappeared to the point that colonies that once contained 100+ polyps are now reduced to maybe a dozen....or even less in some cases.
I have had lengthy discussions regarding this topic with the folks at my local fish store, with little success. I am aware of a type of nudibranch that may potentially feed on zoo's, and I've done my best to eradicate these pests, although a few of them may still linger in the tanks. I have recently noticed a type of starfish, perhaps a microstar, that is often seen attached to the shaft of the polyps. I have included a picture of the starfish in question below. The specimen is roughly 3/4" in diameter.

Is this starfish a possible cause of my problem? Is it the nudibranchs? Is it something else entirely? I have successfully maintained various types of soft and hard corals, with the zoo's as my only significant problem area. I would be forever indebted to anyone who can shed some much needed light on this frustrating subject.