It's really about the level of ammonia/nitrates in the water and a sufficiently strong source of light, that's all that algae need. It will happen to any water

It's really about the level of ammonia/nitrates in the water and a sufficiently strong source of light, that's all that algae need. It will happen to any water that sits a few weeks in open air so that spores can get into it. Even a regular tap water with added chloride will turn green if it has at least some level of nitrates in it (and usually they have).