Hello, I built my greenhouse late last Spring and have had good success so far during the Summer and early Fall. I'm capturing rain water to a food grade 250 gallon container which feeds a water misting system to water my plants. It all works great. My question is, can anyone suggest an organic vegetable food or fertilizer I can add to the water source to help growth? I have to make sure it doesn't clog the watering misters either. Thanks

I wouldn't add anything to the water system - you don't want to spray the plant leaves with fertilizer, you want to improve the soil so the roots can use the nutrients. Fertilizing plant leaves makes plants look better but it does nothing for their long term growth and health. Find a fertilizer and apply it directly to the soil.

If you're catching rainwater off a roof via a gutter, there's already some bird poop (and possibly dog poop, if you have crows, magpies, etc. that carry it to the roof to pick it apart). So the water in your tank might already have a load of bacteria. Adding fertilizer to that seems like a risk. If it's misted on fruit and edible leaves it might contaminate them. In any event, you should wash all produce in contact with collected rainwater thoroughly before using.

I was planning to catch rainwater off a roof to fill tanks in my greenhouse, until I noticed the magpies picking apart dog poop there. Alas! I still catch rain, but use it to water the outdoor garden, shrubs, etc.

This is easy. Go get yourself a couple of feeder goldfish from the pet store, they are voracious eaters and poopers...

you'll have a nice low level of phosphate and nitrogen at all times.