This is my hesitation also. I guess you could build a sort of sump in the filter area and throw a Tee inline before the pump. Getting it dialed so it's not pulling too much or too little would be the trick, however as debris collects your flows would change throwing the whole thing out of wack...
A DIY would almost be better in that you could have a normal pipe fitting for the water return and stick the FF away from the pond....
Looking forward to how you'll set it up around your pond.
Grant