I wanted just an isolation tank for baby fish, post-fry stage, that survived for awhile by hiding in floating plants and surprised me a few days ago. (They're too big to swim out of the side slots, as others mentioned.) But:

--The panel that goes on top of this thing is flimsy AND awkward to remove safely/quickly for feeding. I dropped one edge of the top down onto the babies at one point; glad I didn't hit any of them.

-- The whole rig does stay put against the tank wall without suction cups. BUT it floats with its rim way too close to the tank water's surface, so it NEEDS a top. If it had taller sides that stayed higher above the level at which it floats, that'd help.

-- There are bigger fish in this tank, who were quite interested in all those live hors d'oeuvres they suddenly had a crystal-clear view of. There's NOTHING to shield the babies from sight/stress. The plastic on the bottom and on the side that's not next to the tank wall should've been frosted. The bigger fish would've figured out how to dump this container. I tried modifying it to shield the babies from view but in light of this thing's other problems, wasn't worth the effort.

The babies are back in an ugly makeshift isolator and I'm back at Amazon searching for something better.
____
Edit: For my purposes, the Lee Net Breeder worked much, much better.
I wanted just an isolation tank for baby fish, post-fry stage, that survived for awhile by hiding in floating plants and surprised me a few days ago. (They're too big to swim out of the side slots, as others mentioned. ) But:

--The panel that goes on top of this thing is flimsy AND awkward to remove safely/quickly for feeding. I dropped one edge of the top down onto the babies at one point; glad I didn't hit any of them. -- The whole rig does stay put against the tank wall without suction cups. BUT it floats with its rim way too close to the tank water's surface, so it NEEDS a top. If it had taller sides that stayed higher above the level at which it floats, that'd help. -- There are bigger fish in this tank, who were quite interested in all those live hors d'oeuvres they suddenly had a crystal-clear view of. There's NOTHING to shield the babies from sight/stress. The plastic on the bottom and on the side that's not next to the tank wall should've been frosted. The bigger fish would've figured out how to dump this container. I tried modifying it to shield the babies from view but in light of this thing's other problems, wasn't worth the effort. The babies are back in an ugly makeshift isolator and I'm back at Amazon searching for something better. ____
Edit: For my purposes, the Lee Net Breeder worked much, much better.