Pool to pond?

I have a rectangular 20'x40' inground pool that I no longer want or use. I put it in about forty years ago and now that I'm facing down 65 years old, I find that I don't really use it much and I'm just tossing money at it in chemicals, time and effort.  Last week, as I was fighting with the cover, I was thinking how I really need to do something.
I would like to maybe have it be a pond and was wondering if anyone has converted a pool into a pond and what would be required.  I know that it would need some sort of aeration, and I'd like to have plants and fish if possible.  It does have a deep end, so at least eight feet deep there while the shallow end is four feet.  
I do live in zone 5 central Vermont, where we do have cold winters...although it's not been as cold as it used to be.  We had been a zone 4.  Where we used to get light, fluffy snow, it's now more wet, slushy stuff. Sometimes, the temps will dip to 20 below, but that is rare and when it does happen, it usually only lasts for a few days.  
I mention all of that because of wanting fish.  I'm hoping for that symbiotic relationship between the plants and animals.  Anyway...is it possible to do this?  Has anyone out there converted a pool into a pond?  Is it too deep?  If so, could you let me know what was involved and whether or not you are happy with the results, or should I just hire an excavator to remove the whole thing?

It should be totally doable.  When you have the right balance of plants and animals in the pond, you shouldn't need a filter or aeration at all.  Hardy fish and other creatures won't have issues surviving winter since if the pool is full, it shouldn't freeze all the way to the bottom, assuming it's at least a few feet deep.  One challenge might be adding a shallow water plant zone, which will help with water quality and providing habitat.  A floating island may be a viable solution, unless the pool has a shallow end for children, in which case large pots and other containers can simply be placed in it.

Good point Alder, the shallow zone is important. How about a floating raft with plants filtering the pond?
I've seen those in Amsterdam, tthey do a great job of cleaning the water.
I'd wait with fish or look for fish that do need eat all plants, like those orange koi that destroy kill ponds all over the world.
I have a tiny pond with a great balance between fish and plants, but the fish are not over there in USA.

The pool does have a shallow end which is 3.5' deep or so.  I love living in Vermont, but one of the downsides is that there isn't a huge diversity of businesses, and I wouldn't know how to proceed without help from someone who has done such projects before. (For example, when I discovered Permaculture a few years back, I also discovered that no local nurseries sold fruit trees other than the standard apples, pears, cherries and peaches.  I ended up having to order most everything online.)
Obviously, the pool has electricity to it, but it would be a dream not to have to have anything "plugged in" and have the symbiosis between plants and fish take care of it all.  Frogs do jump in all of the time, and because of my plantings, I do have lots of birds and dragonflies, etc.  A friend suggested tilapia--not something I'd be too keen on, but certainly a possibility as would the koi.
When I went to town and was waiting to donate blood, I went outside because it was a glorious day; there was no place to sit so I walked over to the culverts by the street and was shocked to see about ten crawfish in the water.  A bird must have dropped it from somewhere because it's more or less just an overflow for road runoff.  It would be cool to even be able to raise them!  I've never tasted one myself and have always assumed that they were a southern delicacy....of course, that would mean that I wouldn't want to dip a toe in on a hot day!

That is a great idea for repurposing a pool into a pond.

As I get older I am wishing a had a pool to do exercises in because that would put less stress on my body parts that get to aching as I get older.

Even if you turn the pool into a pond it would still be available for swimming.

Here on the forum we have had some other folks who wanted to turn an unused pool into a pond.  Some because there is less maintenance.

Here are some threads that you or others might find interesting:

https://permies.com/t/65790/Swimming-Pool-Pond

https://permies.com/t/224104/Converting-traditional-pool-natural-pool

I hope you will let us know how this turns out.  Maybe even do a Project thread.

We have an in-ground swimming pool that became a pond. It wasn't something we actually planned, but once my husband removed the fill dirt and it rained, we eventually ended up with frogs, dragonflies, and all sorts of pond critters. You can see photos here - https://permies.com/t/153620/Unexpected-Frog-Pond

Ours has a crack in it so it won't stay full. It's a sunken pond. I've added pond plants and it's really a pleasant addition to our homestead.