How to Kill Gammarus Shrimp?

I have a 30 gal breeder tank meant to breed plecos. My L340s laid eggs 4 times now but the gammarus shrimp in their tank caused the male to either eat the eggs or abandon them by bugging the s**t out of him after which the gammarus devoured the eggs or attacked the egg sacks of the newly hatched fry, not a pretty sight. I have started to remove as many of the gammarus shrimp and the tangerine tiger shrimp from this tank as I could. The tangerine tigers now have their own tank and the gammarus are going into a holding tank with an air stone. This will be an on going process for at least 2 more weeks as the tangerine tigers just had babies and I am still having a hard time finding them all. Once they are gone I would not have any scruples eliminating the gammarus shrimp using whatever means necessary. I could add some CPDs and corys fry to eat the smaller gammarus shrimp and let the larger ones die of old age but that could take months. What would be a better way to eliminate the gammarus shrimp without using fish as predators and not harming the plecos and snails in the tank? I thought maybe adding some copper pennies, but then I don't know how much copper is actually in a penny and would copper hurt the snails? Any thoughts would be appreciated. I have 2 weeks to figure this out.