For most jellyfish you need a kreisel or a pseudokreisel. Look it up online. Pseudokreisels aren't difficult to make. If you struggle to find info I could make you a diagram. The idea is to not have any corners with small angles. Even 90 degrees is an issue, so you have to make it close to circular. You must have a rotating flow. Corners can damage jellies.
Upside-down jellies are a notable exception.
Upside-down jellies are a notable exception.
