Thank you for your response. I ended up using Purple Power with some coarse rocks from my yard and shook the container for a bunch of minutes and a lot of paper towels with a metal rod to get to some of the more difficult stains removed. The solution was also used to clean the outside of the reservoir, which had more stains, using an old sponge with a coarse backing.
After I removed the rocks and cleaning solution and rinsed the reservoir several times, I used the bleach to whiten the plastic and placed the reservoir in the sun to dry and get the benefits of the sun to help with the whitening. After about 5 hours of drying I again rinsed the reservoir and it looks pretty close to new.
Again, thanks for the reply and your point about mixing a bleach with solvents is a valid precaution.
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