To culture green water is simple once you get the start culture, all you need is a container, airstone and lots of light. Then as you use it you top up the container with a 50/50 mixture of freshwater (it can even be regular tap water doesnt have to be RO) and saltwater and it will continue to produce. I keep a small culture going (for no apparent reason) in three 500ml bottles put a small start culture in each topped them up and now i leave them on my patio where they get ample sun, leaving the lids off (i dont even run an airstone on them, just shake the bottles a few times a week), will put a pic up later.