I am considering dosing my aquarium to support coral growth and also to get more corals. I have GHL Profilux 4, and thinking of getting a GHL Doser 2.1 slave with either 3 or 4 pumps - depending on what I have to dose. Unfortunately automatic water changes are out of the question, since I don't have space to nicely store it. I know people dose "2 part" and kalkwasser, and some even dose iodine etc. My tank right now has few corals, and it is a mixed reef, I have some zoas, mushrooms, hammers, candy canes, frogspawns and a few sps, and I am interested in getting more frogspawns, favias, acans and a few more SPS, probably just more birdsnest or something easy.As I understand this would likely be too much for me to continue supporting on just weekly water changes, plus I am well aware automatic dosing promotes growth by keeping parameters perfectly stable, which is why I have decided to buy the doser. With this in mind the question is what do I dose?, and would I need 3 or 4 pumps?, they even sell one with 2 pumps, but sounds like a bad purchase. Any input, suggestions more than welcome, as I am completely new to dosing. Additionally any sensors that I should have that would alert me in the event a doser malfuncioned would be awesome!, all I have right now is a temp probe, I am buying the Ph probe, would the redox, conductivity or oxygen sensor help configure some alarms for possible doser malfunction?. Also if anyone has experience using the GHL Doser 2 or 2.1, I would like to hear how you like it. From what I've read online they are very quiet, precise and reliable.