Lots of Bleach
After finding the wonderful smell of rotting eggs the first year we had our 260, I, too, learned about bleach. I fill the ballast tank about half way, add about 10 gallons of liquid bleach, and then finish filling. Never had a problem.With 2,000 pounds of water ballast, there is about 220 gallons of water, and a lot of organisms that will grow. Using 10 gallons is about a 4% solution, which is a "shock" treatment. I use a large funnel, and it's very easy. I don't have to do anything for the entire summer.Good luck,Ray Trombino"Sand Dollar"