Sorry, I guess I was less than clear. My first pond was tiny and was a liner pond. I got tired of holes in the liner from the occasional accident (dog claws, etc.) , and covered the next, 900 gallon liner pond with a non-structural fibered concrete "skim coat" of about 8" . It worked quite well.
http://www.taniadibbs.com/aspen-oil-...ding/index.htm
I am afraid to go with a concrete or block pool on a DIY job in a place with our soils and winters. I actually posted a question on which type of pond to build this time
https://www.koiphen.com/forums/showth...d-construction
but didn't get too many responses so I just decided to make it the same way again and I think it is too late to turn back now. The main difference between this pond and the last one is that we made a collar on this one that is still under construction.
Yes, it was DIY last time too and the mix had too much slump and collected a lot at the bottom, decreasing the depth a lot. I will get a 2 or 3" slump this time and will also put deer fencing or chicken wire in the concrete to help hold it in place.
I was going to have the skimmer plumbed as well as having the drop in pump, but maybe that is a bad idea. I was thinking of having another external pump like a Sequence going to a filter from the SC's. I am not sure how to make a moving bed bio filter out of a water tank but if you think that is the way to go I can look it up. I used to have one SC only that was made out of a drum with concrete making a cone at the bottom and it worked great, but still I always thought two in a row would be better, maybe with the second one with some filter material in it. I like the idea of turning off the skimmer and waterfall and still having the BD working. Can the TPR's handle the flow from the Sequence 1000 you suggested? Thanks for your response, Tania