Most kids love to have unlimited access to a pool; they would be in it for hours every day if they could. However, parents are not always the same. As you get older, it takes more effort to go swimming in the backyard pool and you probably have many other things you would like to do instead. So now that the kids have left home or are more interested in their hairstyles than swimming, is that backyard pool gathering metaphorical dust? Why not convert it into something else? Something that could become a very interesting hobby. What?
A fish pond! This is not only ecologically sustainable, but you will have a great supply of fresh fish on hand for dinner. We tend to think of a fish pond as something about knee high holding rarely seen fish only a few centimetres long. If your swimming pool was converted to a fish pond there would be no reason not to grow fish to eat in it. It is deep and big enough that many fish would thrive.