Air pump to res size ratio?

Just wondering if there is a generic gallons per hour ratio per gallon of res in dwc setups?

I have a 18g res and am using a 285gph air pump with 4 cylinder air stones hooked up. Bubbles are fairly strong but after my res is flooded with roots im wondering if they're still cutting it since the air stones end up almost smothered by roots?

Hey Butt,

Some growers and experts say that high oxygenation is great and low oxygenation can cause serious problems in DWC. Others say low oxygen is not a problem, many have no idea and no opinions.

With the air pump and bubble stone rig you are currently using, you are pumping about 38.5 cu ft. air or a little over ½ cu. ft. air per minute with 4 new bubble stones that are not stopped up anywhere. http://www.about-air-compressors.com/gallons-to-cubic-feet.html As your new air stones age they tend to stop up and produce less air bubbles becoming less effective.

Conversion = (1 gal air = 7.4 cu. ft. air)

285 gal/hr. air = 38.5 cu. ft. of air per hr. or a little over ½ cu. ft. air per minute. 80% of that total gas volume pumped is Nitrogen.

I would assume that you are not really interested in the 80% Nitrogen component of air and the 20% Oxygen component is your main interest.

Without guessing or hoping, do you know for sure if your all your plant roots and all your bacteria culture is getting the right amount of oxygen continuously throughout the grow period?

A few questions please:

What is your DO Saturation now with the air pumps pumping air?

Do you test your DO saturation with a DO Meter or DO test strips?

And the big question is: What is your desired DO Saturation that you want to maintain continuously throughout months of growing period to the harvest? How much oxygen do you want and need for your crop and all the bacteria to thrive?

Why take chances wondering, simply test your dissolved oxygen saturation and you will know for sure.

I would add in more air stones like twice as many so the pump pushed twelve 4 inch stones.

its a what 100 lpm pump ?

With that much airflow you need enough air stone surface area to pass it *without* causing undue restriction and the subsequent rise in air temperature / tank temp.


After sizing the pumps airflow to the stones lpm gas exchange rate I use ten 4.75 inch stones and two big 10 inch stones with 85 lpm of air from two pumps and 25 gallons of nutrients

look into airstone sizing on commercial aquarium / pond websites for the formula.

PSA: J Henry is just trying to sell you shit.

I have a 10 gallon res and use two 100gph air pumps so 200gph total. My roots are very happy and my girls grow without restriction. If i was in an 18gal i would use 3 or 4 100gph pumps. Certainly won't hurt to add more, hell 100gph air pumps are only $17. I'm sure there is a formula out there but idk what that is and in my research i mostly just came across everyones own opinions