Hi , I collect a lot of rain water when I can from a down spout off the green house roof it goes into a catch barrel then is pumped out with a submersible pump into large trash cans with lids no sun can get to it ,no algae growth .
I put a mosquito dunk in the catch barrel . The trash cans are stored outside with lids in the summer on the enclosed porch in the winter . Also have a trash can in the green house with a submersible pump that I use for watering .
I did store the water in jugs in a dark area to stop algae growth when I grew in the house ...works well .. Gin