BGK, the purpose of the anti vortex baffles are to prevent a vortex from forming in a vertical stand pipe, similar to a hood on a horizontal overflow pipe or a canopy on an angled overflow pipe. When a vortex does form, it can drastically cut down on the flow rate the pipe can handle since it is basically a big air void taking up space where water should be.
I do not currently have an aeration system and the most oxygenated water is at the waters surface. The reason I have an outer pipe around and slightly above my vertical standpipe is so the water that overflows into the pipe is coming from below the waters surface. Normally a setup like this pulls from much deeper than the 24" depth I am pulling from, but since my pond is mostly excavated, it is better than nothing.
Here is the brass antivotex baffles I made yesterday on the top of the standpipe. Tonight I will cut my 15" outer pipe that will go around the baffle, drill and paint it so I can put it in place this weekend.
