Yep Plain tap water and if you have air pump and stone drop that in it will displace the chlorine at a faster pace.Interesting about the tap water. And you mean sit around say in a container with no lid? Also- have you heard about going dark for 36 hours right before going to 12/12? Read that somewhere. I also read its best not to mix the molasses with the nutrients, and to feed them separately mixed with just water. Thoughts?