Best methods for additional oxygen

[KoiCop]

I believe I read that Waddy recommends 40 L per 1000 UK gallons.

[Louie]

Because of the hot weather in July here in So Ca. I added a spray bar to my waterfall. Not only did it drop my water tem but I noticed that by breaking up the water it added more oxygen to the system. Not only did it drop tem by 4 degrees because of the force for the water to escape thru 5/16 holes it made the waterfall look like more water was cascadeing down. I do have a air pump that feeds 6 1" 1/2 air stones . The bonus was dropping the water tem and enhancing the waterfall with the spray bar. No glue so I can go back whenever I want.
Louie

[EmeraldKoi]

There are a few important facts with oxygenation :

Firstly, the myth that the bubbles oxygenate the water. Of course there is contact between the bubbles and the water in the pond, but by far the bulk of the ingress of oxygen occurs between the water surface and the air above it. Hence venturis are not such a great idea.

The trick is to get the water from the unsaturated areas (the bottom of the pond and any 'dead' areas) to rise to the surface and make contact with the air above the pond. Airstones are great for lifting the water of these areas to the surface of the pond, where oxygen rapidly diffuses into the water, which then moves down again as more water is lifted by the airstones.

Place your airstones in such a way to lift water from the bottom and cause a general circulation in the vertical plane. In Japan a number of the breeders use a row of airstones against one wall of the pond ... this causes a sheet of water to continuously rise up one wall and along the surface, to go down again on the other side. This is also good as it does not detract from the visibility into the pond as much as stones scattered about, and is very effective.

I am cautious of venturis, as if they are not correctly designed and installed, the air can endure high shear stresses during the sudden expansion and compression in the venturi, and can go into solution. The same can occur with airstones that are too deep (over 2.5 meters). Air in solution will slowly disolve out and can form fine bubbles, which can make the water look milky, cause bubbles on the sides of the pond, and of course cause gas bubble poisoning. This is when the fine bubbles fizz and stick onto the koi's gills, and block the contact area which the fish absorbs disolved oxygen through. With a fine film of bubbles over the gill area, the fish will actually suffocate.

A proper pond air pump, with the correct airstones, placed not more than 2m below the surface is the answer. Safe as houses, and guaranteed to move the water surface to allow for good oxygenation.

Happy aeration!

[junglegeorge12]

In the heat of summer part of keeping the water oxygenated is temp too. So I would opt for a shower with spray bar. You get everything mentioned above pluc a temp drop from evaporative cooling and added oxygenation points from the huge surface to air ratio in a shower and the many strike points on a hard surface as it falls through. Plus you get more filtration to boot.
I personally don't feel the bubbles from air stones oxygenate very well either. They do create movement though.

[JJKOI]

Thanks for all the Info