Hi Pilot!
We love it when new members ask questions
Copper is not safe for fish, if you have them in your pond. If your pond is only plants, then this tip is great for you.
As for size, it really just depends on the amount of water, so giving you a definite answer is tough. A few pennies work in a birdbath, so try to scale up from there
Make yourself at home- there's lots to learn on ATP
