So I will be coming into possession of a shallow (~3' deep) 1000gallon fiberglass and plastic aquaculture pond.

With this pond, I want to set up a long term breeding/evolution experiment, similar to a Creatures wolfing-run (I won't be able to be quite that hands off, as there will need to be basic pond maintenance and feedings). I'm just not sure what stressors I want to put on the guppies to force a change over the years.

Things I have thought of:
>incrementally increasing the salinity of the water over the years, to eventually ocean levels (can become staggeringly expensive)
>incrementally decreasing the temperature of the water to eventually breed cold water guppies
>incrementally decreasing the amount of light to breed blind guppies
>severely limiting the food input into the system to see what food stress produces (not so stressed that they all die)
>just doing as close as I can to a true wolfing run, just minimally maintaing the system and seeing how fat and happy guppies become

I don't want to do the "breed a huge population and then introduce a predator" experiment. Been done A LOT with guppies.

Guppies reliably produce about 3-5 generations a year, and I have roughly 60-70years left to live baring any unforeseen accident. That is enough generations to get to see some sort of cool change in them.