Threadfin Rainbows are so effective in exterminating these scuds and so do the Least Guppies. I had 75Gallon planted tank where literally millions of scuds swam in open freely , every nook and cranny and root were infested with these guys. The 7 Threadfin Rainbows, 7 Least Guppies, and 5 Dwarf Cajun Crayfish eliminated them to extinction in less than 3 months. I was shocked actually. When I removed the tank of fish, shrimps, and crays the scuds never ever again returned this was 1 year ago.
The Threadfin Rainbows will actively and efficiently hunt the babies since their mouths are so small
The Least Guppies will eat babies and juvies very efficiently and actively, night and day non-stop. Seriously these guys don't know when to stop.
Least Guppies are very intelligent and will investigate constantly where the scuds are hiding, due to their curious nature unlike the regular guppy too dumb to find food unless it is waved at them.
The Dwarf Cajun Crays will hunt the adults in very nook and cranny they can crawl into(adult scuds too big for the Rainbows and Guppies)