Wait, thinking about it... Not half way filled because that might look weird, but maybe filled up to where the first step of the pool is. That way it's not filled all the way and I could at least walk down into the pool without getting wet. For some reason the idea of the pool being completely filled with water freaks me out. I've lived with this empty pool for all these years that the idea of it being filled with water is actually frightening. Unless there's a good reason, why does an unused pool need to be completely filled with water anyway. Am I making any sense? I need advice.

I did end up going for it. See link below. The pond gradually slopes down one half with a deep end of 2.5' (and an extra 1' overwintering hole filled with sand/leaf litter). Marginal shelf around 80% of the pond (blueflag iris, pickerelweed, golden club, arrow arum, cattail, etc.) planted into clay soil left over from excavation. The overflow runs into a "bog" area (just dug down about 1', laid out some excess linear, and put soil/sand/peat mix back in) which stays wet for a day or two after rain (red lobelia thriving there). Had a string algae bloom in the spring, as expected, until duckweed took over the surface in early July. Added some toad tadpoles from a drying up puddle in May, and they're now 1-2" toads that are out and about at night. At least 10-20 damselflies buzzing about the surface every time I check, and the rest of my garden beds are also loaded with them. No fish, no pumps or filters. Have a rain barrel set up next to the pond but haven't had to use it all summer, especially with the duckweed. I used mosquito dunks from spring into early summer, but haven't put one in in over a month. Despite my concerns going into it, I can say this is the most mosquito-free summer we've ever experienced. The pond has become everything I hoped it would be in less than a full season. Here is a link that might be useful: This post was edited by c2g on Mon, Aug 4, 14 at 23:16

Waterbug guy, First I will talk a little bit about concrete in water. You say it is a myth that concrete in water can kill fish and raise the PH. When concrete first sets up the surface PH is 12.0. Which is the same PH as a drain cleaner called "draino". As it is exposed to the CO2 in the air the PH goes down. But water is a very good leaching agent and so water will continue to try and get the chemicals out of the concrete. So will the PH in the water be raised? If the water has normal PH of 6.5 to 8.5 the answer is yes. The real question should be "how much will it raise it"? That question isn't easily answered as there are a lot of variables. Just to list some the age of the concrete, the condition of the concrete, is the water flowing over the concrete, the natural PH of the water, is the water being changed, and the volume of the water versus the contact area of the concrete. In some cases the rise might be so low as to make it very difficult to measure. But in other cases it can and does raise the PH to 9 to 9.5. At these levels it can and does kill fish. If I remember correctly you have stated that you are a pond contractor. If you are I hope you having started using roofing liner in the ponds that you build. Most of the time a person on this forum is never going to have a problem with roofing liner. Can there be a problem with roofing liner? This should be the question. The answer is yes. The chances that there could be a problem is very low. The largest pond product manufacturer in the US sent out a letter to all their customers a number of years ago. This letter said that all their liner in the future would be tested to be fish safe as they got a batch in that was not. In other words they were selling roofing liner as pond liner. This company had been selling a lot of liner for 10 years before this problem. If it had happen today with the wide use of the internet I would have think that some lawyer would have gotten this information and started a class action lawsuit against them and they would be out of business. The lawyer could easily have sued them not only for the cost of the liner that they had sold but for the cost to replace all those liners in the ponds built with them going back to the first time they sold this liner. The largest liner manufacturer in this country has told me that almost never would you ever have a problem with roofing liner but you might. I think that as a contractor you can't take that chance. If you were unlucky and did have a problem and were sued over that problem the lawyer handling the case would find out that they would sue for every customer that you have that has this liner. In other words you would be out of business. So is roofing liner toxic? No most of the time. But there is a small chance that there maybe a problem. I have only talked about 2 of the 8 things that you listed. I could easily talk about many of the other things listed but my point is this. You listed these things as black and white but they are not black and white. The only thing that is black and white about ponds is that all aquatic life will die. Mike

Marlene, the filter will work in the sense it will remove turbidity - just as it did for a swimming pool. However, whether or not you replace the sand with new sand won't matter in the long run. First, the pressure drop across the sand bed is high (compared to biological filters and other systems often used for ponds) which requires a much higher horsepower pump to operate. Second, the filter will plug rather rapidly requiring frequent backwashing possibly more than once a day. Back in the days when we had a swimming pool I remember that the amount of water to backwash the filter properly required quite a few gallons. You could redesign the system to use things such as bioballs, etc. but the inconvenience for access, the problems of rebuilding....I guess I'd use something else. You could put it out by the pond, take the top half off and use it as trickle tower (fill with loose, plastic straps or other biofilter media and let water flow over the top of the media and out the bottom of the unit back into the pond - if you want a nice, shiny art-object out by the pond. :-) ---David