[Don Ro]

I want to plant a few trees that don't like the salty Arizona water. Avocado tree, for example.
Thinking of catching the rainwater off my roof into something like a lined hole in the ground...a pond.
I don't know, maybe several hundred gallons or so.
I'm concerned about the water getting sour, mosquitoes, etc.
Any suggestions as to how I can keep the water clean enough for plants/trees w/o creating an eco system w/fish and plants?
.
Right now just thinking about this. Who knows what will eventuate?
Maybe too much drudgery.