Im skimmer-less too and I too have 4 fish, the biggest is a 3 imch long engineer goby and a have a pretty good cleaner crew too but my corals all seem to be doing great, they are growing to the point i can tell visually about every 2 weeks, its not much in 2 weeks but I study my tank so hard lol guess its all part of being new. i just do water changes alot, ill usually do small ones probably every week instead of the one big one every month or 2 weeks and my water seems to stay quite stable and healthy. i check it regurlarly too, basically once, a day before a water change and then after