I can provide air pumps, tubing, stones etc.
Give me a bit to get them up on the site (and I can probably get other sizes of stuff if necessary but I’ll start off with the things I have already used myself.)
The vague rules of thumb I’ve been operating under for the last several years are, you want about a cubic foot of air per minute for each 400 gallons of fish tank. It takes aprox 1 psi to push air through the air stone and 1 psi to push air down under each 28 inches of water depth. So for a 300 gallon tank that is less than 28 inches deep, look for an air pump that can deliver .75 cfm at 2 psi and you should be good. Make sure you get enough air stones rated for the amount of air flow that will be available at the water depth you will have since restricting the flow out of an air pump by not letting it go somewhere will heat up the pump and shorten it’s lifespan. See the air stones have a rated amount of air that can pass through them in a given amount of time.
Now if there is plenty of water flow a system might not need supplemental aeration from an air pump but I always find, especially in our warm summers, that the fish eat better when there is extra aeration and the extra water movement provided by the air bubbles tends to help move the solid waste out of the fish tank and off into the grow beds. Too much air would be if you are boiling the poor fish out of the tank with the bubbles or when there is no water in the tank. I also find that in the bigger systems, it might be too much to run the water pumps on the battery backup but running an air pump on battery backup is within reason.
So, I’ll be working on adding items to this product category and in the mean time, contact me if you need anything related to Aquaponics Aeration and I can work up a price for what you need and let you know.