My friend had to work last weekend so I've postponed the trip until I can catch him on a free Saturday. There's really no rush to collect them, they are always in the substrate.
Not all jellyfish need a round tank. Some are passive and spend most of their time anchored to a location. I'm keeping a type of small blue saltwater jellyfish that does great in a regular rectangular tank. You do need to protect them from being sucked into a pump or filter or fish stomach!
Those aren't real jellyfish. They are a protozoan that just so happens to look like a jellyfish. They need a species tank and a lot of food meant for feeding fry. Just because they aren't jellies dosnt mean that they aren't cool, however. They breed easily and make awesome aquarium inhabitants