They are not difficult to keep, although you may have to do profilactic treatment periodically due to the nature of their diet, as well as the difficulty of spotting issues with them due to how they look. Their skins have a lot of growth on them, and it's hard to tell if they have any parasites, ich, etc. They are ok in terms of getting exo-parasite/fungal issues due to their skin and the fact that they shed pieces of skin periodically, like the rhinopias and some others.
They prefer darker sand as it makes their camouflage work better, although I have one that is so white and red, that he kind of stands out in black sand. I've had a darker goblin in pink hawaiian sand, and over a week the whole upper body of the goblin looked the exact color every time he'd burrow in.
Longest I've kept one was 2.5 years, and died due to electricity failure and 90 degree tank water. The longest I've had one of my current ones is 1.5 years. All 4 of my current ones are eating both live and dead. I mostly give minnows, goldfish and guppies, which I keep and feed reef food and marine pellet diet. They also love krill and silversides. The smallest silversides in the bag are good enough for 2.5-4 inch goblins, and the larger pieces can easily be eaten by a goblin at 5" or more. I like to alternate to keep them hungry, but in my experience eating's never been an issue. My old boy even ate some lionfish, a grouper, and a small mantis shrimp, and lived to tell the tale. You do have to maintain a regimen of feed and starve. They have similar afflictions to the anglers and frogfish and you have to let them digest their meal fully before feeding again.
I used to keep a Goblin in a tank with 3 mantis shrimps, a crocodile fish, dragon wrasse (4th one of these was too large to eat lol) and a Shy Hamlet. All of them leave him alone, except algae scraping tangs and rabbits.
Currently have 4 of them of various sizes in a reef tank, with a popeye catalufa, sailfin tang, rhinopias, flashing devil, a couple lions, some wrasses, a grouper, angler, that sort of stuff.
I have lost 4 of them, too within the last 5 years. 1 to electrical failure, at least 1 due to too much feeding, and 1-2 died when my water was in a horrible condition.
I can easily say they are my favorite fish. Having more than one lets you observe some unique and peculiar behaviors, such as congregating at night, or walking behind each other like a cargo train. They seem to be communicating with each other in some way, and always group together in weird ways. Smallest is 2", then 3.5", 3.5" white/red specimen who is usually the loner, and the 6" one.