Why? Is this an aquaponics project? I doubt if they would do good since they will rot in the garden if they are too wet. They are nothing but baby onions that you slice to put on a burger.
They're def different from "onion plant" type bulbs that are actually aquatic. I think rodger is probably right, unless you really had the right setup beyond just sticking them in your sump.
yep here is a fyi... the cool thing is you can grow these onions and celery and scallions and leeks from the root part you throw away if you set up an aquaponics bed .. just fyi.