If you are into cephalopods for the haul, your best bet is to get a ro/di unit. I started out lugging water from the pet store. I carried home 1 gallon jugs. I then switched to 5 gallon pails. The best investment I ever made with keeping marine tanks is a 4 stage ro/di system and a 200 gallon bucket of good salt.Im sure you can do with some tap waters or a simple 2 stage ro/di unit however.....To be honest,nothing makes me feel better about the quality of my tanks than knowing the water I use is the most pure it can be, these animals can be very sensative water conditions. O.bimaculoides is a very hardy species. You could encounter a more difficult unknown species someday and good water quality may make a difference.