What should I do with my old water for my water changes? I am on a septic system so putting it down the drain is NOT an option unfortunately. With my freshwater tanks I have a 50 foot siphon that drains into the yard from the house, but putting saltwater in the yard is not a good thing so that option isn't available either. It is only a 40 gallon tank, so at most it would be 20 gallons, but with decor and whatnot, it would most likely be closer to 15 gallons. Any ideas?