dwarf puffers or small gouramis decimate them. they are slow methodical hunters and seem to be the most efficient IME. you will never get rid of them completely without tearing down the tank and sterilizing everything, but dp or small gouramis should keep them in check.
I have found scuds to be a challenge when trying to eraticate them. I had them in my 1.5 gal shrimp tank. I tried various fishes, some - like the gouramis will keep them in check but they do not totally get rid of them.
I also tore down my tank and boiled the gravel and bleach dipped most of the plants, ans scrubbed down the tank, filter, and everything else. They still came back (i suspect the HC was hiding some). They survived several weeks in a uncycled tank with the ammonia,nitrites being very high.
I ended up ditching any plant that could not be bleach dipped and freezing the tank and gravel and filter.
Good luck on getting rid of them!
This is what dhavoc on the planted tank forum stated about scuds.....
"you dont want to mess with them. yes they are easy to breed as feeders, but they are also IMPOSSIBLE to eliminate from any tank they are introduced to. and remember, they are plant eaters (especially mosses). and the big negative... if they cant get enough food, they WILL become carniverous, they have wiped out my opae ulae tank (yes they can adapt immediately from fresh to brackish water). they also will attack newly molted shrimp.
they are not worth messing with, go with daphnia if you need a live food source. scuds are just too hard to get rid of. "
Thanks for all the suggestions....I am going to put some german blue rams in for a week and see if they help..it not then I will completely tear down the tank and start all over...: )...came across "El Natural"..maybe give that a try....since I have some plants from my 240g tank.