RUGF:
Reverse Under Gravel Filter.
To aim the water flow into what is normally the up tubes of an under gravel filter. Water is spread out under the plates and flows up through the substrate. Goal: keeps debris out of the substrate and enhances the water flow so the gravel works at an enhanced rate as biological filtration.
I tried this on quite a few tanks. Debris always settled under the plates in the front corners. The PH pushes the water down at the back of the tank, generally in the corners. Most of the force of the water is gone before it goes even halfway across the tank, allowing the debris to settle through the substrate. Cleaning is pretty easy, though. Remove the intake from a gravel vac, or just use some vinyl tubing down the up tubes and suction out the debris.
PH as water moving device (w/o media): Look for Circulation Pump, something like the Hydor Koralia. A lot more water movement for the power used.
PH as filter: Some models can have some kind of media installed on the intake side. It will plug up pretty fast. I use the coarsest sponge I can find, just enough to keep bits of leaf out of the PH. Leaves can clog the intake. Even so, finer debris will get trapped and can stop the water flow.
PH with alternate installation:
See this article. You can add more complex filter media to the intake end of the PVC. To make it actually into enough to be a real filter it takes up a lot of room in the tank. I would prefer to add another external filter such as the appropriate sized Aquaclear filter (not the power head). This will add water movement and keep the tank more open for the fish.
https://www.loaches.com/articles/hillst ... -fast-lane
If you really want floss media filtration, I would not use a power head. You want a slower water flow over a larger area to allow the debris to stick to the floss. The faster the water flow the more debris gets knocked off the media. If you can spread out the water flow over a larger area then the debris is more likely to stay trapped. Again, an external filter that allows you to select your own media is better than a PH for filtration.
38 tanks, 2 ponds over 4000 liters of water to keep clean and fresh.
Happy fish keeping!