Ok. So if I follow your advice and I use 3/4 pvc we run the risk of the barrels not draining fast enough. If I put 1/4 valves on the incoming water lines though to each barrel I can micro manage the flow. And to keep from dead heading the pump then with the restricted flow I can put a Y in coming off the pump and use the excess pressure/volume to run a fountain or additional water fall.
Dead heading is the fastest way I know to destroy a pump.

Now we start draining the pond to start redigging it. Time to make it deeper, possibly a split level pond to increase DO and the larger the volume the more constant the parameters. Bigger is better.

Once excavation is complete, I will build a short wall around perimeter from railroad ties. They are cheap, and the liner will keep water from contacting. This raises water level, increases volume....but running the pump intake off a skimmer in middle of pond ultimately reduces head pressure on the pump.

Water will go from main pool of pond w/skimmer. To IBC tote. Coming in at the bottom, and as the water level rises, near the top will be the pipe going to the GB. No pump needed there as will use the gravity. Water to GB. Then out the siphon to the highest pool of the pond and will discharge in the form of a water fall, flow through the split level pools and back to the pond skimmer....and repeat.

This will allow me to move roughly 6500-6800 gallons with one pump. The uppermost pool can be used as a grow bed as well. It's a preformed pond liner that I have previously installed at an angle and once full overflows one side as a waterfall to main pool. So no siphon there as it's a flow through currently full of lilies, etc. I might take this out and rework it though.

I need to push this design around some more. I feel like I am forgetting something.