This is more of a totally differnet idea then a modification to my design. The concept of a submerged water intake with controlled air-intake concept is the same, the method of solving the problem is totally different and impressive.

This picture shows the standpipe installed and working inside a hang-on overflow chamber box.

The design as pictured is handling about 300GPH but I think it could handle more then that.

Here you can see how simple it is to create this design. From left to right the parts are:

1) End-Cap.
2) Stand Pipe with holes drilled in it.
3) Slip Reducer.
4) Coupling that the slip reducer can fit into.

Note from Ken Stockman: I have redesigned the water intake on the small pipe ( where the water exits). Instead of drilled holes I used a miter saw to cut a 1 inch square hole in the pipe. This will stop small pieces of debris from getting stuck in the pipe intake.

The Slip Reducer (#3) has been slid over the standpipe (#2) and the End-Cap (#1) has been placed ontop of the standpipe. Ken drilled 3 small holes of 1/16 inch in the end-cap. Start with one hole and add more holes to the cap as needed.

The height of the standpipe is adjusted later based on how high the water level in the overflow box needs to be.

The Coupling (#4) has been slid over the Reducer Bushing (#3) and the design is completed.

Just insert this into your overflow box and try it out.

Your tank may be a special case and may need to be modified IE: you might need more/less holes in standpipe, you might have to try different stand pipes heights to see what works best for your environment, you might have to play with the hole size in the End-Cap.

But it remains that this is very easy, cheap, and fun way to make your overflow boxes quieter.

I would suggest you include removing the standpipe for cleaning as part of your monthly tank tasks to make sure the holes are not getting plugged.