I don't really know what to do. I have gammarus scuds in my shrimp tank and they are starting to cause problems. They are leaving my RCS alone for now but they are just destroying my duckweed roots. Along the bottom of my tank I am starting to see the roots just lying there where they munched right through it. I tried adding a rosy barb into the tank for about 15 minutes but instead of going after the scuds, it was just gorging itself on the duckweed and leaving the scuds alone so I took her out. I currently have two berried females that have about 3 weeks before the eggs hatch and I was wondering if there was anything I could do. So far I've heard of removing all the shrimp and "gassing" it with CO2 but I'm not really sure if that will be enough. Also, would that kill my biological filter? I am using a sponge filter and the up-tube is crawling with them. I'm worried that they are going to become carnivorous and attack the newly hatched or even some of the newly molted RCS shrimp. Also, the only CO2 that I have is DIY that I use in my other tank so I'm not sure if that would be able to produce the necessary results. The other option I can think of would be excel. Would a massive dose of excel be sufficient to kill any scuds in the tank?