Gush Catch pen looks beautiful and effective, but the throat is too small for scuds, it's always out of stock and it is pretty pricey. here is my free version
My attempt. The little plastic tubs are the ketchup containers from my local Arby's. A short piece of air hose, wire paper clip heated with lighter to melt a hole in the bottom. The plastic tube with the blue cap is a Petsmart "free water test" vial, it will become version 2 if this works well.
top and bottom of finished product
In the tank, baited and flooded. We'll see if I catch anything! Had to put a little gravel in it to keep it down. Thinking I might use this to catch baby cherries for transport, just set it on it's side.
Left it in the tank overnight - caught a scud! and a bunch of tiny little snails
A design revision though - the scud was alive and kicking at 4:00pm yesterday, dead this morning. Opened the top and the water had a smell, I think a combination of too much food as bait decaying and no O2 in the water since it was sealed (except for the little tube).
Cut a big hole in the lid, closed it over a piece of window screen. Makes the lid tough to get on, but should provide plenty of water exchange and keep any caught critters alive.