Res aeration... how much?

So... 200 litre (45 gal) low profile res.... how much aeration is required?

I have a 4 outlet aquarium air pump and i plugged 2 lines and ran air stones on the other 2 in the res. The amount of bubbling seems insufficient. I thought of unplugging the other 2 lines and adding stones, but i guessing that the pump just doesnt put out enough pressure to make much difference.

But maybe im wrong? I just dont know how much aeration is required?????

Use aquarium style pumps rated for 20 to 60 gals. The have two air outlets keep your res temp in 60s or high 50s and your good.

I don't think you can add to much O2 to the res('s). But, if you supplement the CO2 to your room, (usually at a rate of 1500- 2000 ppm) you should consider bringing in outside air ( at approx 350- 400 ppm CO2) with your air pump to add to your res's. It's no good feeding elevated CO2 to your roots, that will cause root rot as well. The object is to increase the O2 in your res, not the CO2.

Gquebed said:

So... 200 litre (45 gal) low profile res.... how much aeration is required?

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It also depends on what kind of system you are running.
If you have an external reservoir for E&F for example, you don't need any aeration.
For DWC, look at how agitated the surface of your water is.

Just setup a small pump to make a water fall. Done deal. Air stones will make the pH fluctuate.

If running flood and drain it's a non issue as @Keesje stated.

Renfro said:

Air stones will make the pH fluctuate.

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As I understand it is the CO2 in the air (leaving the airstones) that causes the fluctuation of the pH.

Keesje said:

As I understand it is the CO2 in the air (leaving the airstones) that causes the fluctuation of the pH.

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yeah, I avoid them. Carbonic acid I think... but a waterfall seems to oxygenate without the pH flux and it circulates your nutes allowing you to mix in additions. Airstones will work but you will be fighting the pH drift constantly.

O2 gets into the water because of the airpressure: The weight of the air above the water pushing down on the watersurface.
When the surface is moving (like with a waterfall or flooming) the O2 will get easier into the water.
Flooming and waterfalls are very effective to get maximum DO. As long as the surface is moving.

Many people think that it are the airbubbles from an airstone that get the O2 in the water. But a large part of the DO gets in the water because the bubbles reach the surface and create motion of the surface.

Someone said "If you just look angry at water, oxygen will even be dissolved"
Sounds funny, but he is almost right. It is so easy to get maximum DO.

Waterfalls are generally more efficient at aerating a res, I would say do that if you're capable of it. If not, old fashioned air pump and stone will get the job done. As far as how much air if you go the airpump route, all I can say is that more is better. I use a 110lpm air pump and use it to run 4 5 gallon DWC buckets, all of which usually have 2.5-3.5gals each and it seems to provide a great amount of aeration. In combo with beneficials, I've never had root rot with this setup. Only challenge will be is cooling the water unless you have a concrete floor like I do, or a chiller. If I didn't have concrete floors, I'd probably look into a waterfall setup personally.

Did you ever try a normal pump, put it on the bottom of your reservoir and make it circulate the water? Or face it upwards? I will guarantee you that the amount of DO will be the same as with the other systems.

Your problem is the volume output of the pump does not meet the requirements of the airstones. People incorrectly think a Gph is needed. You need to match the equipment and all that's required is that you have good surface agitation over the whole surface. It's not the amount of air going through the stones that provide the DO its the surface agitation that provides gas exchange. Smaller bubbles are better at this not because they dissolve easier in water that's a myth 02 is extremely hard to dissolve in water at or above equalibrium.

added: you could simply use smaller air stones to solve this issue as long as you are still getting good surface agitation of the whole res

I just let my flood trays waterfall back into the res when the trays fill. I stopped using airstones in E+F about 7 years ago now.

Thundercat said:

I just let my flood trays waterfall back into the res when the trays fill. I stopped using airstones in E+F about 7 years ago now.

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Yeah when the water drains out of the plant sites air gets right into the roots unless you use rockwool. But with expanded clay pellets the draining water pulls air into the rootzone.