Thanks for all the new responses guys, I still need to try netting them while feeding and maybe the dark thing again. But the soda bottle thing definitely does not work for this type of tetra for some reason, I don't know why the pristellas arent even interested. My tank is so heavily planted, that maneuvering nets in any way is very difficult. Its not going to be easy, but I will try something tomorrow and let you guys know how it goes.
Bridroid- it should work if you put their favorite food in the trap, and the hole is big enough for them to go in.