Hi, I'm building my first pond and it's been a great learning experience so far. Here's what I've got done so far. The pond on the right side of the walkway will have a curved wooden bridge to access the outdoor kitchen. I originally was going to only have a small round 400-500 gal pond on the left side of my stone walkway. After digging it and filling with water and staring at it for a few hours while sitting on my porch visualizing the finished product, I decided it would look way better if there was also a pond on the other side of the walkway, to give it the effect of looking like the stone walkway was a suspended bridge over a single pond,so without much more thought, I got up and started digging away. After a while of digging, I tired so I took a break and went and sat back in my chair on the porch. While again looking at the pond, I decided it would look super awesome if there were also some big fish swimming around in it so I decided it would be a Koi and Goldfish pond. Now I have to dig it even deeper and make it bigger. I'm also digging under the walkway so I can connect the two ponds with a 12" pvc pipe that the fish can swim through. So now according to my calculations, it will be around 1700-1800 gal. I'm thinking down the road, I might turn the 4 raised stone planters above the wood planters into fish-less water gardens/bogs and circulate the pond water through them. That way I could have a huge amount of plant filtering and the fish would not have access to eat the plants. This was my test fill to make sure the used epdm liner didn't leak. I've since drained and removed the liner and am excavating the hole bigger so the depth goes all the way to the walkway edge to give the appearance that the water goes under it. The sides of the pond along the wood planters will have a small shelf for edge plants to hide the liner and the exposed liner on the shore by the rock stairs will have a wood deck over top so the pond looks like it goes under the deck. I'll also be building a concrete bench on the stone wall behind the deck for sitting. I decided that each pond will have it's own pump and filter, to create a dual pond system so that if one pond fails in some way such as pump going out or whatever, the fish can just swim through the connecting pipe to the other pond until I can get the other pond going again. I like redundancy. The bio and UV filters, and pumps will be hidden under the wood deck on the right which has a hug 4' deep hole under it. I forgot to mention that there will be 4" pvc pipe cut in half lengthwise under the stone walkways wood edging which will attach to the pond liner somehow and channel the water underneath and to underneath the deck where the skimmers will be hidden. Another option would be to just extend the pond liner under the wood edging and not use pvc pipe for the channel. Anyway, still got a ton of work to do but it's been a lot of fun building this so far.