If i were you if you really want to do SPS try a monti digi, or a monti cap....i started with these then worked my way to birdsnest, then Milli's and now im starting to introduce acros. Another tip for SPS is if their usually green or red they are easy, any other color requires more work. About the dosing...many ppl dose kalkwasser b/c of how many corals they have, or the more expierenced dosing method is 2 part. Usually if you have miniscule corals you dont need to dose, but as you add more your alk and calcium start to drop faster than nitrates phosphates etc.... For example i dose 2 part every other day, i found out that my calcium and alk where getting absorbed by the corals faster than the nitrates, so now that i dose I only do WC when the nitrates or phosphates raise enough to it could hurt corals. Now since i dose it maintains constant parameters and helps corals grow faster, but as long as you dont have a abundance of corals monthly or weekly WC should do. Polyp extension is another thing that comes and goes. Ive seen SPS with amazing polyp ex that barley grow, and ive seen SPS with no extension and grow like crazy. Just b/c theres no extension doesnt mean the coral isnt doing well, for example my flame angel loves to sometimes get a little nip at my SPS but not enough to hurt it, he does make the corals polyps not extend sometimes but they still grow at a decent rate. I know i guy that lives near me with a ponape birdsnest the size of my head that has no ex whatsoever but it keeps growing like crazy. But if the coral is bleached thats a different story....but like a said theres many things that are different in everyones tank and you have to find out what it is.