Starfish/Urchin compatibility

[surfthreeeleven]

I have 2 tanks I will soon be merging into 1 150 gallon tank... In one tank, I have an african red knob star & choc. chip star, and in another I have a black long spine urchin. I know that the stars can and will devour urchins - is the long spine included? I've read about tuxedo's and pincushions getting eaten, but will the longspine be in danger too? Also, I feed both starts 1Xweekly with krill...

Thanks!!