Why deep water culture needs bubbles

In deep water culture, plants float on foam rafts with their roots hanging in a deep tank of nutrient solution. Roots need oxygen to take up nutrients, so air pumps push bubbles through air stones to keep the water close to saturated, and warmer water can hold less oxygen at the very moment roots want more.

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Floating raftsPlants sit in net cups pushed through foam boards that float on the solution, so the crop rides on the water itself.
Roots in the waterRoots hang in the dark solution all the time. They are surrounded by nutrients, but they still need dissolved oxygen to breathe.
Air stonesAn air pump forces air through porous stones. Fine bubbles give oxygen lots of surface to dissolve into as they rise.
Warm water squeezeAt 30 °C water holds about a fifth less oxygen than at 20 °C, while roots breathe about twice as hard. That is when root rot often starts.
Pump offStop the bubbles and the roots slowly draw the oxygen down. In a few hours a warm tank can drop below what lettuce needs.

Oxygen falls as water warms

The oxygen readout uses a standard curve fit for fresh water at sea level: DO = 14.652 minus 0.41022 T plus 0.007991 T squared minus 0.000077774 T cubed, with T in degrees Celsius. It gives about 9 mg/L at 20 °C and about 7.4 mg/L at 30 °C.

That is the most the water can hold when fully mixed with air. Real tanks run a little below it, which is why bubbling never stops.

Try it: slide the temperature from 18 to 30 °C. The water's oxygen capacity drops by nearly 2 mg/L while root demand roughly doubles, and the plants start to yellow. Many growers chill the solution to the high teens or low 20s for this reason.

Demand rises too

Root respiration speeds up with temperature. Biologists often use a Q10 of about 2, meaning the rate doubles for every 10 °C rise. The demand readout uses that rule of thumb relative to 20 °C, so it is a simplified teaching model rather than a measurement.

Sources

Electrical Conductivity and pH Guide for HydroponicsOklahoma State University Extension
Active aeration enhances tissue hydration and fresh mass in hydroponic lettuce and modulates calcium-mobilizing biostimulant efficacyScientific Reports, via PubMed Central
DOTABLES: dissolved oxygen solubility tablesU.S. Geological Survey

How to cite this model

Avid Solutions International. (2026, November 11). Why deep water culture needs bubbles [Interactive 3D model]. Avid Field Lab. https://avidsolutionsintl.com/explore/deep-water-culture

Last updated November 11, 2026

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