At the risk of sounding negative, this is quite a project for even a professional pond builder, much less a homeowner.

That being said, here are a few items for consideration.

1. No need for a 12 foot depth. 5 feet is sufficient for a Koi pond.

2. You have not specified whether or not this will be a bare liner or Rock & Gravel pond. It will make a difference in the required size of the constructed wetland (gravel) filter.

3. For the proposed configuration, you will need at least 2 pumps and 2 skimmers.

4. Depth again. Constructed wetland filters need not be more than 1.5 feet in depth. This is the maximum root depth penetration that you will get from any desirable aquatic plant(There are some that you will want to avoid.).

5. 45 mil 'Fish Safe' EPDM liner is available in factory seamed sizes up to 200' x 50' Weighing roughly 0.30 lbs/sq.ft., EPDM liners can get quite heavy and require considerable manpower to install.

6. The size (volume) of any supplemental bio-conversion, biofilter or constructed wetlands, should be based on the projected ultimate fish load (weight) and not on the size of the pond. Keep in mind that the pond itself (total submerged surface area) serves as bio-filtration.

These are just a few items to consider in your proposed project. Much, much more would be involved.

Last edited by Instar; 11/05/13 12:54 PM.