Ask-a-Dave's-Gardener: Water tank question , 5 by Ifdb

Ifdb wrote:
Hi my awesome son built a greenhouse for us.I have 2 water tanks for future needs .they had vinegar in them ,came from a baker.I filled them about 3 weeks ago . They are now growing a scum and are greenish in color .Is this safe for future watering ? Is there something I can do to correct this without draining them? I live in md.zone7a and it\'s been warm ,inside greenhouse temperatures up to 100 or more during the sunny days plan on using drip lines when it becomes to cold to use outside hose .thanks