Ok. Let's start saying that acans are my favorite corals. But I have a small problem. I have a 25 gallons tank plus 15 gallons sump. It is 24 inches long and 15 inches deep. 3 inches sandbed plenty of love rock tank is Almodóvar 3 years old 1 blue tang and one yellow tang lives there from the very beginning (yes I know but kind of bonsai tangs) I have about 20 different acan lord and a few zonas and palys. Heavily feed with marine snow zoplan and photo plan By 2 little fishes and kz lps aminoacids and kz coral vitalizer and ocasional target feed with lps pellets from fauna marin I have lot of new heads but ACAN POLYPS DO NOT EXPAND I have tried a lot of things but I can't get the POLYPS expansion I saw in Other aquariums. My lightning are 4 ati 2 blue plus one purple plus and one aquablue special. My skimmer is a reef octopus sr1000 very efficient and I turn it off after feeding. Any ideas? Please help