My experience changing to reverse flow
I went from a regular flow on the 20 gallon tank with an undergravel filter. I had it set up with a power head sucking water up one riser tube and the other riser tube was powered by an air stone.
I recently decided to switch to reverse flow which sucks the water through a filter into the power heads and blows the water and air down the riser tubes to oxygenate the beneficial bacteria that is under the filter plate). This has resulted in a very cloudy tank due to the detritus (uneaten food, plant material, decaying matter) under the filter plates to be blown into the tank. Within an hour I had a layer of mud 1/2 inch deep on top of the gravel.
I am combatting the detritus that is being kept suspended in the water by the reverse flow by doing water changes and eventually it will even out.
My suggestion to any who consider reverse flow as an option is to start your filtration system that way and stick to it as changing later on will get debris in your tank.
The fish and plants are very healthy as are the shrimp.
With an undergravel filter with two or more riser tubes you need to run all the the pumps in the same direction (either forward or normal flow, or reverse flow) or you defeat the purpose of having the gravel work as a filter as the water will take the path of least resistance.