Hi again. I'm glad to see this thread alive.
I've had a few frogfish over the years. I've had my current one, a pictus, for two years and nearly 6 months.
I have him in a species only tank as far as mobile animals are concened. There are a few soft corals in there with him, with a single pc actinic and a single white no bulb above.
I wouldn't recommend any crabs or fish with a frogfish because for one thing they can damage his esca (lure) by trying to eat it, and large fish could nip, tear and bully the smaller frogfish, or end up half-in the mouth like others have related depending on size. The other obvious reason is blockage or internal damage to the frogfish. Another reason is that lionfish and scorpionfishes can damage their lower jaw, which is a very sad thing to happen. (Similarly, however cool it might be to feed live food to a predator, many snake and large lizard owners only feed dead mice and rats in order to minimize the chance of damage to their pet). I've also had trouble with large hawaiian starfish trying to eat one of my frogfish before. Microstars are probably fine, but I wouldn't trust any predatory starfish. As for snails I've had a much oversized mexican turbo in with my frogfish but I wouldn't put anything he could even think of putting in his mouth (even enough to damage his jaw) in the tank.
As for feeding I feed my frogfish and my dwarf lionfish (in a different tank) every 3 or 4 days. I vary their diet between uncooked shrimp and ocean fish from the grocery store that I cut a chunk off of. Once in awhile I'll feed them krill but thats rarely. I never feed any pieces larger than I think their gut would be, and definitely not anything larger than 1/2 the length of the fish I am feeding - more like 1/4. I always soak the food in a tiny bit of rodi or tankwater with a drop of selcon directly on the food for awhile before I feed.
I use a feeding stick someone suggested on rc to me a long time ago. I posted a picture of it in this thread somewhere. It is a thin rigid airline tube with a short section of flexible airline tube forced onto the end of it. A fishing line fed through all the tubing until just a quarter inch or so of fishing line is sticking out. On the other end of the tube you can make some type of handle to tie the fishing line off on. I tied it to a piece of larger tubing that I rubberbanded to the side of the rigid airline tube. The way to use this feeding stick is to spear the food with 'hair' of the rigid fishing line sticking out of the end of the tube. You stick the fishing line 'nub' through the food. The whole feeding stick is pretty clear, especially in the water so it works pretty well with a bit of puppeteering of the food. The soft section of flexible airline tubing helps prevent damage to the predatory fish's jaw if he tries to gobble the stick accidentally. You can also pull the handle you tied the fishing line off on with your other hand if you have to , which will retract the fishing line from the food item.
The other thing I think is most important is water changes and keeping the water clean. Most people keep frogfish in a small species tank which doesn't take long for the frogfish to end up living in his own unflushed toilet. This becomes even worse if you are feeding coral in the tank periodically like I do, and have live rock with its own bio-mass. I've been planning on getting a drilled tank so that I can plumb my frogfish tank into my main reef tank's sump so that it will benefit from the large water volume, skimming, and easy water changes.