star ployps coral

Ok so awhile back I got a frag of star polyps. After reading up about them I learned that they are very easy to grow and can over take a tank. So I placed the frag on a rock and kept the rock away from the main rock structure of the tank. The rock is now completely covered in the polys and they...

Ive had these for about 3-4 weeks now and just last week I saw one little polyp come out for a while. It doesn't look like it's doing to well now though, and i noticed a white spiderweb looking collection on the bottom of the coral.

I recently added some coral to my tank, which has been running with fish for about 6 months. First I added star polyps. They stayed open for a few days but have not opened now for over a week. I also added some mushroom coral which started really well and seemed to love my tank....for one...

I guess I need to face the fact that I need to prune my Star Polyps. I am not iterested in fragging or selling I just want to restrict the growth. Can I shade areas where I want to restrict growth or do I need to physically remove the coral? Are there other otptions? Thanks