What Gast pump are you looking at getting? My 0523 (1/4 HP) likes to run 3 diffusers nicely. I think 2 would work well, but one may not be enough to handle all the air flow the pump can put out. I know the Vertex diffusers can take 2 plus CFM per head, but they are rated at 1 CFM (EDIT: 1 CFM for the liftrate flows), so that is where I run mine.
What diffusers are you going to use?
A 1/2 acre pond is around 1 million gallons and you want to turn that water over in a 24 hour period, or less. A single Vertex diffuser would do that in as little as 6' of water (almost double at 12'), but a 1/4 hp Gast pump would be trying to push 3CFM or more through it. It would be better to run 2 diffusers, or 3 ideally (given the 0523 pump).
Consider putting a diffuser in an 11-12' depth near the 14" hole and a second one midway between the first diffuser and the next farthest bank. This helps cover the whole pond and reduces the stress on the diffuser membrane. I am speaking theoretically with regards to stressing the diffuser. I have accidentally pushed 3 CFM through a single diffuser for a short period and I know it can take it, but I tend to error on the safer side and shoot for 1 to 2 CFM per diffuser for long term use. I say to not put one in the 14" hole just in case the hole could act as a cool water refuge below the thermocline. Some folks manage this in larger ponds for heat relief during a hot summer. After looking at you photos...it dawned on me that you may be using this pond for swimming and not necessarily fish. If that is the case...I would drop a dual diffuser into the deepest part and size the pump for that number of diffusers and depth.
Given a bit larger budget for some additional weighted tubing, fittings, and an additional diffuser...add a third one to the pond. A pump of similar in size and design could easily turn your pond over in a 24 hour period and leave room to only run part of the day (or night).
Post your pump and diffuser choices and we can get into some of the calculations that I have generalized above.
I was looking at the GAST 0523 like you referenced here
https://www.septicsolutions.com/sep...523-rotary-vane-pond-aeration-compressorI was also looking at the dual membrane diffuser here
https://www.septicsolutions.com/sep...rane-diffuser-assembly-for-pond-aeratorsBut now after seeing some comments I wonder if I would be better served buying 2 independent diffusers like shown here
https://www.septicsolutions.com/sep...rane-diffuser-assembly-for-pond-aeratorsI definitely want to use this pond for fishing... it's going to be a swimming/fishing pond until my wife decides swimming in it is no longer fun
So the question remains then.. if it is a good idea to run 2 diffusers, should I put one in the 14' hole and one midway from the next farthest bank, or put the deeper one in closer to 12'?
Also, am I picking out the right pump and diffusers for the job? I really appreciate all the guidance here!
