Maybe use a cucumber slice, wait for the plecos to go on it and try to scoop them up with a net. I never tried it with fish, but it works with snails so it might with baby plecos.
That's definitely worth a shot. I could catch a bunch when they were smaller & less aware. Now they're about 3/4 of an inch & have caught on to my tricks haha. It was a huge spawn, probably 60 - 70fry
Place a large cup In the tank on its side.
One that is a solid Color and they can’t see you.
Rubber band their favorite food to a rock and place it inside the cup.
Mine prefer zucchini.
Once there’s a bunch feeding you can place a net over the cup and scoop them up in the cup the net is just to keep them from escaping.
This way they Don’t get caught in the net and risk damaging them.