Take a look at adding artificial structure, there are ways to make the bottoms smooth so not to puncture the liners. You could contact fishiding or mossback artificial structure, there is a segment on different types of DIY to add to your pond that would benefit your pond.

Do you have a layout of the pond?

In the archives theres a section on structure that many have built, maybe you get some ideas from there to put in your pond.


laugh
Good land management is an extended learning experience-Aldo Leopold