I have enough 45mil epdm to construct a 20' x 10' pond. Initially will start with comets as we are close to a river and want to see wildlife interaction before investing in koi. I will hand dig and hope to have 3' deep for wintering. The removed ground should make a nice berm for a horseshoe waterfall. There is 1 infant Ginko tree to provide some shade, but I know when it developes it will have huge leaves. I need recomendations on skimmer size and features for potential koi pond and also to house a suitable pump that will be approximately 20' away from falls and hopefully 4' high. Furthermore, I would like to use more than 1 spillway and am curious if they all need to have filtration. Would 1 biofalls and some simple spillways cause a filteration problem. Any input would be greatly appreciated since prior to this I have only had a small preformed pond with bottom filter and pump.