I'm going to be getting ocean water for my fowlr and using that pretty much for filling and all water changes. (I know I know.. the debate about doing this) I will be going about 1-2 miles or more out to collect the water to make sure its pretty pure.. but one thing I keep thinking about is evaporation. I will still need to top off with fresh water every week and was trying to avoid having to get an RO/DI... any ideas on what else I can do for my top off water to keep it simple? I also was open to ideas on what I could collect the water in and transport it back by boat, if anyone can think of something that would seal decent. I would need to do the first fill up about 100 gallons and then only about 20 gallons for my water changes. I didn't want to have to do multiple trips for the initial fill up.