Make sure to use a good surface skimmer before the water gets to the return pump. The skimmer will double the life of your pump. Although a good pool filter will work, most are DE filters and they will clog very quickly. They are just not designed for the type or amount of mechanical filtration you will need in a water garden application. Look into a large water fall filter or a bubble bead filter. The other thing to consider is the liner material and what effects your dogs getting in and out of the pond will have on the liner. Remember if you make it easy for the dogs to get in and out of the pond you have also made it easy for raccoons, cats and everything else you don't want in the pond to get in. If you have any questions feel free to pm me, I was the head designer for Hill Country Water Gardens for almost three years before I opened RCA. I even designed two "dog" ponds.