Elodea - bottom or shelf?

no1catman

I have a pond about 3.5m x 2.3m in size, it has 40+ mature goldfish, with pump and filter system. Given that what is the best position for elodea (Canadian pond weed)? On the bottom or on a shelf - maybe 0.25m deep? On the bottom - the fronds will spread out and up - but can they be drawn into the pump? While, being on a shelf they just grow outwards, but with (to my mind) less spread! 
Any comments, thoughts, personal experience.

onwards&upwards

Nowhere, its an invasive non-native species.