Thanks for stopping by.........
My rainwater is collected right from the downspout on the side of my home. As a result, anything that was laying on the roof or brewing in the gutters winds up in it. This includes dust, seeds, insect larve, and a host of other things. No, I don't really think any of them would effect the plants, however, a warm highly oxygenated hydro tub is the perfect breeding environment for many of these things, especially mosquitoes. Additionally, If I carefully filter it, before I seal a five gallon jug, I've found that I can store it right thru the winter with no ill effects. This gives me access to a supply of rain year-round.
As far a stretching goes, I do get a bit but have found several methods to keep in in check. First off I raise the tubs on newly introduced plants by placing another inverted pot under them. This gets them much closer to the light source until they are well established. I also keep my light and dark period temps within just a few degrees. This helps to keep the internodal lengths as tight as possible. And lastly, when changing a plant over from 24/0 to 12/12, I do it in three or four steps each a few days apart. This too will help to reduce stretch.
"I was so much older then, I'm younger than that now"