Looking for some help and ideas for a pair of ponds. The first pic is what I have now in front of the house and the second Is what I have in mind. I plan to have Koi and goldfish as well as a few plants along the edge in the top pond 9'x10' 4-6' deep aprox 3300 gallons with a bottom drain. The upper pond will overflow with waterfall and stream into the lower pond 6' lower will be another pond maybe 8'x8' 3' deep aprox 1400 gallons. mainly for plants and might have a fish or 2 that get from the top pond into the lower Top pond I was thinking of having a 4" bottom drain - 55 gallon prefilter with 300 micron screen - sequence 750,4200 pump to a tpr and possibly a skippy filter in a 70 gallon stock tank with a low ( 12"??) water fall return or 2-55 gallon s&g filters. Bottom pond A skimmer and bottom drain to 55 gallon prefilter some sort of 55 gallon drum with possibly strapping or matala mats sequence 750,4200 pump up to the top pond with a low waterfall return. A valved return to the lower pond for cold weather to bypass the stream return from the upper pond to the lower. I would prefer to run 1 sequence 4000, 5600gpm pump instead but I think the 2 pump system will be safer and not allow any chance of the top pond back flowing down the pump and pipes into the lower pond if a check valve leaks or fails and power outage. Wondering if I should have an undergravel filter in the lower pond instead of a bottom drain and strapping filter? Any ideas or advise on this setup would be great, like the diy filter ideas and have room below the deck for barrels and pumps.