I have read on this site that FHM likes to spawn under long horizontal things,,,,, I am thinking of putting logs or 4" drain pipe on top of cinder blocks..... how deep in the water can i set these? 2 feet, 4 feet ? 6 feet? Thanks

Close to shore in water 2 ft or less is best. Pallets are a good choice.

Definitely shallow, if you have steady water levels stick with less than a foot. If your pond tends to drop in level, maybe two foot to make sure your spawning structure is still usable during the summer. FHM in ponds with predators will rarely go deeper than a foot...