I am wondering how i go about getting water for my weekly water changes. I need to use RO water for it but my nearest supplier is about 45mins away so i dont really want to be driving there every weekend. Can i buy several drums of it at once and store it, leaving the caps screwed on? Or is it something that needs to be gotten fresh?? I realise i can buy an RO unit myself but that would have to follow on at a later date. Cheers