I installed my system last year with the diffusers about 2' off the bottom and have added 18" to that height (3 weeks ago). I still have a muddy looking pond, but I am not convinced, yet, that it is from aeration. I no longer get light plumes of muddy water when the air is turned on, since adding the extra height...my pond just looks muddy all the time. My diffusers are built like this...
I have added an 18" nipple to the above and mounted the diffuser to that.
If I can convince myself that my system is causing the muddy water I am thinking about adding a flat base to it, maybe 3 or 4 foot square piece of corrugated plastic. I really hope that I don't have to try that as it would be hard to handle that big of a contraption when pulling them up for cleaning and inspection.
