Basically just a little rust. No need to have it shipped. Iron is an essential nutrient in plants needed for photosynthesis.

Hydroponics requires flood & drain in most cases. Loads of plants can't handle having their roots under water all the time, bubbles or not. If you sit the pot on a 5 gallon bucket and let the stuff drain into there, you can keep cycling through the same tea until you need to change it out. Just do it with the same frequency as watering.