I’ve had a pictus for almost a year and it was ~ 1” long when I first acquired it (him?). You may try getting some live ghost shrimp which you can hold by the tail so the head is facing the frogfish and so it can move a little and attract attention. Use some large forceps to hold the shrimp by a very small piece of its tail so when the frogfish strikes, it will grab the shrimp from the forceps and swallow it. If you hang on too tight, it may only get half of the shrimp and let go or spit it out. After doing this for a week or two (I feed 2-3 times per week) you can try substituting krill or large mysis (Piscine Extreme brand are large) that was formerly frozen in the same way. It seems the frogfish is built to strike at food with full force, so you want to ensure whatever you are feeding is held by a very small amount and the force of the frogfish sucking the water in will pull the food from the forceps and it can swallow the whole thing. Once it is used to associating the forceps with food after a couple of weeks you can substitute other food items (I’ve fed silversides, pieces of squid, cuttle fish and octopus). I would not suggest starting to feed it by letting some live food items loose in the tank, thinking it may take even longer to get it to eat from your hand or forceps/feeding stick, but after while I like buying a chromis or peppermint shrimp on occasion so it can hunt.
You mentioned about putting it in its own tank which is a good idea. They are utterly defenceless, relying complete on camouflage and will definitely eat your smaller fish and inverts. I have min in the refugium section of my 40g sump with lots of live rock and macro algae. You have a really nice frogfish, outstanding colour. There is a great thread on RC dedicated to these guys with lots of good info called the Frogfish Files you may want to check out.
