Catching fish in a plant tank

I loaded my 125 gallon tank with juvenile Apistos and Corys that
I brought back from a collecting trip to Peru last year.  Now 
they are big enough that the tank is getting overcrowded, and I
can actually measure nitrates, even with a very heavy planting.
I know I need to thin the population, but I've never figured out
a good way to catch fish without totally wrecking the plants in
the process.  Any advice?