Here’s my long, bloated story. Hope it helps. I, too, thought this was a piece of junk when I initially tried it out. In truth, I was hasty to watch the jellyfish dance, and didn’t soak the tank for 24 hours (presumably for signs of leaks?), or soak the jellies in hot water for 10 minutes, or even run the pump beforehand. I did, however, attempt to get the bubbles out of the jellies. Anyway, nothing happened. Jellies just floated at the top, and the pump didn’t seem to be working (at least, not very well). The pump is, btw, supposed to come on and off every 8 seconds (says so in the instructions). I ran it for about an hour, still nothing.
I was about to return it to the store when I read on the internet to add dish soap. So, I added a little bit (maybe 1/2 tsp). Then I took a chopstick and really beat the jellies senseless until every last bubble was out of it. They actually sunk to the bottom of the tank, which they hadn’t the first time around. I then lined up the pump in the back until it was exactly in line (and the two black pieces fitted into each other snugly). And guess what? After a rush of bubbles, my jellies were zooming around the tank. Not as graceful as the real thing, but they were “dancing” nonetheless.
This is a pretty cool little conversation starter, but not sure if it’s worth the money, or the trouble, honestly. The pump can be pretty loud, and the jellies I got with mine look nothing like in the picture. Still, it’s the closest looking thing to the real deal and I did find myself transfixed on the little guys.