“The last thing I wanted to do was grow jellyfish, are you kidding me?” says Brock Gratton as he looks at the hundreds of live moon jellyfish occupying a dozen tanks on the floor of his office. Still, he and his twin brother, Blake, have spent the last year perfecting JellyTank, their desktop jellyfish aquarium. The brothers, 35, who also own Sarasota’s Xplode Marketing, presold 1,200  JellyTanks in May.

JellyTank started last year on a whim. “I was redesigning our website,” says Blake. “I saw some jellyfish and thought, ‘That’d be a cool [design element] to incorporate.’ But Brock says to me, ‘Jellyfish have nothing to do with Xplode Marketing.’ I was like, ‘Maybe we can order a tank.’”

When the jellyfish aquariums they found online proved both expensive and impractical—a $400 model kept sucking the creatures into the filter—the entrepreneurial duo designed their own. After consulting with dozens of marine biologists, aquarium businesspeople and other experts in the jellyfish world, says Blake, they reached their $25,000 Kickstarter goal in three days.

JellyTank’s water pump and circular shape create a water flow to mimic tidal movement. The tanks start at $199 online, and the brothers, who grew up in Bradenton, are working to get distribution to retailers and may add employees. They hope to expand to larger tanks that can accommodate more exotic jellyfish species. For now, even before shipping a single product, their sales are pushing $200,000.

Says Blake, “If you would’ve told me a year ago I’d be in the jellyfish industry, I would’ve been like, ‘What?’ The only jellyfish I’d ever seen were in the Gulf of Mexico.”