Nice pics, venwu (DON'T LOOK, LESLIEEEEEEEE, worm killing in progress....).
Conus catus are probably the hardest of the fish-eaters to keep, maybe because they don't transport as well. They live in high-energy, well-aerated water, and it's difficult to duplicate that in shipping. The ones you had in Hawaii would have probably settled down so that you could feed them, but they might not have survived the trip back. Your best bet for bringing them back would be to wrap them in damp towels rather than trying to keep them in aerated water.
Conus striatus are tougher, and are hard to kill. They are also easier to feed, and can survive in fairly low-oxygen, low movement tanks as well as in high-energy tanks. Conus tulipa like highly aerated water, but they are fairly hard to kill also. They are more picky about what they eat than C. striatus, and can't catch as large a variety of prey.
Even though they are probably the second most deadly, Conus striatus make pretty cool aquarium residents, and are the easiest to keep and transport. I'll see if I can't get one back alive.
Cheers,
Don