I just bought a home with a 20'x40' inground swimming pool in poor repair. I have removed the liner and want to use it for a koi pond. My initial plan was to fill the deep end so the bottom is level at 48" from the top coping so the water level would be about 40 inches. I would like to use the pool skimmers and returns (2 skimmers and 3 1 1/2" returns) but have heard that using these are usually problematic. I thought that I would backfill the end farthest from the patio to within 20" of the coping and about 10' from the end of the pool and put a dividing wall there and use that area as a bog filter. I want to also use a 150 gallon skippy filter behind that end and also use a 12" deep bog filter 16" wide all along the side (on the old pool skirt). This would be planted to help with aesthetics as well as filtering. I was thinking I would also install a 5 tier 4'x2' shower filter. I don't know if this is filtering overkill or not but I have had lots of trouble with Algae in past ponds and don't want to deal with it in this one. Any ideas or help would be appreciated, especially if you have experience with pool to pond conversions. BTW, I still have the old closed filter system from the pond that sill words, was just concerned about the cost of operating the pump.