Find out flow ratings on it. Submersable ide say a pondmaster hydrive. If your gonna knock o hole in it a reeflo hammerhead would rock or a reeflo dart would work. Ampmaster dolphin would be ok too.
You're takin all the fun out of building your own custom pond though... Lol
You're takin all the fun out of building your own custom pond though... Lol
).
. I've paid more shipping than that for bags of gravel. 
