My favorite
growing medium is coco chips, and that's what I used in the 5 gallon bucket broccoli
drip system. Coco coir and coco chips are basically the same thing, their both made from coconut husks. Both coco chips, and coir hold moisture very well. The difference is the partial size, coco chips are small chunks about the size of small wood chips you would use in your BBQ. Coco coir has a consistency more like potting soil or peat moss. Both are pH neutral, so they wont change your pH. Just make sure you rinse it real well, just to wash out most of the color. It can color/tint the
nutrient solution. The color wont hurt the plants or anything, it just looks better to me in the long run.
The brick in the picture is a 2 cubic foot block. I usually fill the bottom of the 5 gallon bucket about 1/3 of the way with cleaned and sanitized rock to add weight, as well as aid in good drainage. Doing that, that one 2 cubic foot block is enough for 4, five gallon buckets. If you don't have a local hydroponic shop, you may be able to find it at a nursery. I recently noticed our local ACE hardware store carries it. It's also used as a landscaping ground cover.