Our pond is dirt based - no liner. It was a former cellar under a small building but kept filling with water. The previous owner filled it up with rocks. We tore down the building, rearranged the rocks and let Mother nature take over. The pond filled with water. Our gutter water runs into the pond to help keep it full. We have an overflow running under our driveway and down a hill to keep the pond from overflowing. Fish and one now large water lily are doing well. A filtration system was added 5 years after the original set up. Muck is a problem so a few years ago we removed the fish and sucked out all that we could. Instead of using small rocks again, we replaced them with various sizes of field stone. We have 30+ fish and they seem to thrive. We never feed them. Our situation is unique. This pond somehow links underneath our patio as the fish winter under our patio. They swim through the rocks and re-emerge in the Spring. We have no idea what is under our patio. . how much water is held. . how deep. .but we know when the pond gets low the fish disappear. I do add tap water during the summer months as the pond does evaporate rather quickly. It's not likely the chlorine will hurt the fish as I add it in gradually over a few days. Sometimes I put dechlor in but usually I am careful not to add too much. Our tap water has never hurt the fish that are in there. In fact, as the water is added, the fish swim underneath - possibly enjoying the cooling hose water. This pond is approximately 10' x 10' and 2' deep.

Thank you for the encouraging message, chas045! I hope they didn't completely get killed, maybe just snipped back a bit. It was this way-early warm spring we had and then WHAM! But as a pretty new gardener (with new plants I have little experience with) I am like a fussy first time mother. Any little sneeze and I fear a major illness!!!!

Well, if you are going to just use the 2.5 acre pond to "fill" your garden pond it won't be too big of an issue. However, if it is going to continually be used to power the waterfall etc (IE a big loop) you will infact be filtering the ENTIRE 2.5 acre pond. I doubt that would be effective, or cost efficient. I think you need to have 2 systems both closed off from one another.

The lilies will grow fine in 42" water. As Gary mentioned if they are newly acquired and already have leaves on them raise them up and then lower gradually. Put them on the bottom for the winter and leave them there next spring. They will reach the top and do fine. Of course there is no problem with keeping them closer to the surface if you want. It's just a matter of choice. It may be easier to maintain them (prune and remove old blooms and dying leaves) if they are closer to the surface.