Maybe you should see if your LFS has or can get live feeder shrimp. It might help stay away from "unnatural" type feeding stock like goldfish (which I am not really a huge fan of). It also adds a variety aspect which is always good
. If it were me, I would try to get it on the frozen stuff ASAP once it gets a bit more settled, maybe another week or 2. I just hope it stays happy and doesn't decided your lion fish would be a good snack. I have heard in some cases (depending on size of course) that the stones will try and eat the lions, and both end up dying....oddly enough not from poisoning, but rather the stone ends up choking to death because of the lions spines. Is the lion about equal size? If so, I wouldn't worry as much...but if it is considerably smaller, I would definitely be concerned and perhaps start to consider removing the lion from the tank. This way both fish have a better chance of survival.
Most fish like these do best in a species only tank (a tank where only the one species of fish is introduced and possibly any compatible inverts). In your case it would mean keeping only the 1 stonefish in the tank and very few select non-crustaceous inverts, since they do eat shrimp and the like, as well as other fish. So cleaner shrimp and chromises...(cromi?
) would be a "no no" unless you wanted to feed him an expensive treat
. So I am thinking you might have to stick with mollusk types, but there is never a guarantee he won't try to sample them either. I have a lawnmower blenny that has now decided he wants nothing to do with algae and will only take mysis shrimp...
.
Just out of curiousity, what kind of filtration are you using for your tank currently?
Once again best of luck. I hope it all works out
.