This is just from my experience. If the green stars are young, you won't have much problem. As they grow they get more aggressive. At least they did in my tank. (just a side note: if you don't want the green stars polyps to grow over everything in your tank, keep them in the substrate). The mushrooms and the ricordea will do ok with one another but one will eventually try to outdo the other if they are touching. My ricordea get mad if my red mushroom touches it. Kenya trees (again depending on what you have) are pretty toxic and will need to be placed a little ways a way from anything else (I ended up getting rid of mine). Xenia depends on what you have. Frogspawn should be way a way. Zoa's pretty much just sit there in my opinion and don't have many problems with other corals. Again, this is what I have going on in my tank and this is what I am going on. These things are animals and as with all things that are animals you never know so you just go with observation and what you know about them. What I have learned in my tank is that they need a good amount of space in between to grow. When they get bigger, they start having problems with one another and start doing chemical stuff against each other. I just recently had a problem with a sun polyp being placed near (not next to) a pectinia coral. It had a fit and wouldn't open for days until I moved it and changed the flow to go the other direction.