el guappo, looks like those are Chrysoara... sea nettle. Could be pacific or japanese, I can't tell without colour. either way, those are planktivores. no light needed. still, for viewing purposes, you'd think they'd light it better than that.
OCDP, most jellies need kreisels (full circle/oval) or pseudo kreisels (semi-circle) because they need to stay in the water column. To do this, they are somewhat buoyant and photoactic (swim to the light) but rely more on water current to keep them up than anything else. In a standard tank, they will inevitbly hit the bottom agian and again and wear themselves to death basically. btw the circle/semi circle of a kreisel is not a vertical cylinder (like a can), it is an upright circle (like a wheel). the theory behind the kreisel is that the circular flow keeps the jellies in the middle of the circle and the higher velocity water around the sides keeps the jellies off the glass. not a dumb question, many don't even know what a kreisel tank is, let alone what it's for.
casseiopeia don't need kreisels because they are not pelagic jellies. kreisels might actually be bad for these guys if the kreisel isn't big enough; they need to be able to sit on the sand without being piled on one another.