A Pleco cave set up with a long piece of natural slate, 2 square caves for the ends and 6 assorted caves. Driftwood not included. 

The 6 caves will be selected at random. 

When setting up a pleco breeding tank do not fall into the trap of buying the caves you like the looks of. Every male and (sometimes species) is different. Give the males lots of choices of color & shape and good things will happen. 

My rule is at least two caves per pleco and stacked at least two rows high. My typical 40 breeder will have 24 caves plus lots of driftwood to break up sight lines.