Energy needed to run a sand filter is high. Many big filters use a two speed pump for backwash as you mentioned and in the process lose a lot of tank water. I've cleaned koi pond sand filters and you need a stick to chip it loose. The pressure in the chamber compresses it to a solid block. Which lead to gas bubble disease in kois. Air gets compressed in the sand filter allowing bubbles to enter the koi's blood stream.
I could incorporate an air blower to break up the media prior to backflushing but this chamber is small enough that pumping 50-100g through it should clean it good. Most of the tanks on MFK are several hundred gallons. We'll see.
