Dear Glug,
The most misunderstood concept among pond owners is aeration. The reason is most frogs that breathe air don’t understand the gas laws. Dr. Boyle (1662) found the entire planet and all on it depends on a simple equation: PV = PV. The equation means the pressure times the volume of one gas in a miscible medium must equal the pressure volume of another gas in the same medium (why it rains and you can breathe). In a pond, the gasses are carbon dioxide, ammonia, hydrogen sulfide and methane. In air, the major gasses are nitrogen and oxygen with water floating in clouds. To get oxygen into a pond, you must replace the pond gasses. Because the pond gasses are heavier than water, they are on the bottom of the pond. And thus because they are there, to make PV=PV, you must diffuse air to the bottom.
The first objection I get is: “My fountain draws its water from the bottom of the pond.” The pond gasses are dissolved in the water and are drawn from the bottom, and fall back to the bottom. No aeration has occurred. Likewise waterfalls do little in replacing the pond gasses with oxygen. You cannot move water and get oxygen into it.
The only way to do this is to use Boyle’s Law using diffused air pumped to the bottom of the pond. Exactly what happens is the diffused air will replace the pond gasses with oxygen and nitrogen aerating the pond.
The placement of the air diffuser is important. The best diffusers are sintered glass. If place at the deepest point in the pond, the air will mix with the pond gasses and be lifted out. A gas bubble leaving a diffuser is about a half millimeter and when it reaches the surface, it is a centimeter. This pushes a lot of water where a large doughnut shaped current is formed. This aerates a large volume of water establishing a current in the pond.
I have seen many configurations of diffusers and placements. Many are eight inches off of the bottom or placed in a 5 gallon bucket. The pond gasses are on the bottom where if you are above the bottom with your diffuser, you are not removing the pond gasses. I have also seen diffusers placed above the deepest point in a pond. They do not work.
Froggy, I understand that fountains and waterfalls are important for us as they are beautiful. However, do not be misguided to think they aerate a pond. When you draw a froggy breath, understand Dr. Boyle was thinking of you. Use his wisdom.
PonDoc from the pond