Just so you know, Fanny Mae and Freddie Mac each have line items for pool care that they will pay for if the agent is on the ball and submits invoices. Some brokers don't seem to be aware of this.
When I made an offer my foreclosure (which had gone completely black) I'd looked into this, talked to the Fannie Mae folks, talked to the selling broker, and convinced them to winterize the equipment before we completed the agreement. They paid in full. As a result, though I bought a swamp, I'd bought a swamp with perfectly working equipment and got another 5 years out of my old heater and even longer out of my pump
But this was not just because I'd "negotiated." It was because I drew attention to their own policy
So maybe if you look up the sherrifs auction info or get the bank name from your local records, you could convince the bank to afford a small service budget for which I believe they can get reimbursed. Or do this through the selling agent.
At the very least, they will cover or tarp the pool, depending on whether there's a cover onsite. That may somewhat reduce the mosquito/frog phenom, or at least the eventual smell.