I had a well planted tank once that I didn't want to move the décor out of. It took a year before I caught the last Danio... now those little suckers are fast!
That's the problem I've got! I'm going to try to catch two small platies in my 120L tomorrow, wish me luck, I'll need it!
I'm going to try the old trick of tempting them to the surface with food and see if I can nab them before they detect the trap. Once they get wind of a net they'll disappear into the undergrowth and I might not see them again for hours.
Then poke several holes through the top and the bottle and use something like small wire ties or a bit of string to hold the two pieces together. Put some of the fish's fav. food inside the bottle and submerge it in the tank down to the bottom and wait. Fish swim in and have trouble seeing the way back out. remove trap and cut top free and pour fish into whatever ;-)