The water provides natural fertilizers in nitrates. I can testify that fish water equals or outperforms purchased plant fertilizers. This technique can win points with a spouse who doesn't fully appreciate all the aquariums. Someone discussed the technique of using two-liter Coke bottles as a brine shrimp hatchery. In short, the two-liter bottle is tipped upside down and an airline is connected to the cap.
Air is forced into the bottle to keep the water in motion.
When it's time to harvest the shrimp, the air is disconnected and within minutes the baby brine are gathered toward the bottom with the eggs' shells adrift at the top. At this point the airline is used as a siphon to harvest the brine shrimp. I believe in beautifying our tanks and the quarry offers an incredible selection of sizes, shapes and often color and pattern. Then for that matter, why not just go to a river and hunt for free rocks. When the fish stands still count the grid length of the fish.