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.
Last edited by Quarter Acre; 11/15/21 01:16 PM.
