Hydroponics and soilless culture

Nanobubbles held dissolved oxygen in solution for weeks

Oxygen nanobubble water raised dissolved oxygen (DO) from about 8 mg/L to more than 30 mg/L and kept it elevated for up to 70 days in trials reported by Ebina et al., 2013. In a hydroponic reservoir, the aim is to make the solution itself a store of oxygen for the roots.

The difference lies in bubble size. Air stones produce macrobubbles and microbubbles (1–100 µm) that rise quickly to the surface and burst, so gas transfer is inefficient and each bubble stays in the solution only briefly. Nanobubbles (below 200 nm) have negligible buoyancy and move by Brownian motion, and were reported to stay suspended for weeks or months without off-gassing Ebina et al., 2013.

The 70-day figure describes the conditions of that study. A working system, with roots consuming oxygen, open channels and changing temperature, is a different setting, and DO has to be measured where the roots are.

Warm solutions hold less oxygen

Oxygen solubility falls as water warms (Henry's law), so nutrient solutions in warm greenhouses carry less DO just when roots respire fastest. The result can be hypoxia in the root zone.

A review describes nanobubbles as a promising way to retain DO in outdoor hydroponics in hot climates, where conventional aeration struggles to keep oxygen adequate Foudas et al., 2023. This is a review's assessment; the lesson cites no measured comparison of DO against temperature.

Root health: dissolved oxygen and root-zone pathogens

Oxygen in the nutrient solution supports root health, and a review links it to lower susceptibility to root pathogens Mamun & Islam, 2025. Plants kept at high DO (6.6–7.4 mg/L) were less susceptible to Phytophthora than plants at low oxygen (below 1 mg/L). In hydroponic tomato, oxygen supplied by bubbling reduced Pythium colonization of the roots.

Oomycetes such as Pythium and Phytophthora thrive in stagnant, hypoxic zones. The review attributes the effect of oxygen to roots that can sustain their own defenses, to conditions less favorable to the pathogens' swimming spores (zoospores), and to aerobic conditions that favor beneficial microbes. It proposes that nanobubbles, by holding DO high, would extend this effect Mamun & Islam, 2025.

The Pythium result involved oxygen delivered by bubbling, not nanobubbles specifically, and both results come through a review. Dissolved oxygen is one root-zone condition among several; it does not replace sanitation, clean water or an integrated pest management program.

Biofilm in lines and reservoirs

Nanobubbles have been studied as a way to limit biofouling in agricultural water distribution systems Xiao et al., 2020. Biofilm in pipes and emitters can harbor microbes and clog the lines that deliver nutrient solution.

Two mechanisms are proposed. Physically, nanobubbles create shear at the liquid–solid interface, and their oscillation and collapse are thought to produce micro-jets that dislodge extracellular polymeric substances (EPS) and detach biofilm from pipe walls Babu & Amamcharla, 2022; Xiao et al., 2021. Chemically, bubble collapse is thought to generate low levels of reactive oxygen species (ROS), including hydroxyl radicals (•OH), which degrade the proteins and polysaccharides of the biofilm matrix and damage bacterial cell membranes Shiroodi et al., 2021; Xiao et al., 2020.

These mechanisms come from a biological aerated filter study, a review and tests on food-contact surfaces, not from hydroponic roots. Roots also carry beneficial microbial films, so line hygiene and root health are separate goals.

Ozone is a separate tool

Ozone is an oxidant, not a source of oxygen for roots, and its use in nutrient solutions is a different decision from oxygenation. Tamaki et al. studied how hydroponic leaf lettuce and komatsuna grew when the nutrient solution received ozone microbubble treatment Tamaki et al., 2020. Whether plants are harmed depends on the dose, so ozone treatment needs dose control and monitoring of its own.

Growth results in soilless systems

Air nanobubble treatment increased the aerial fresh weight of Brassica campestris by 27% to 34.5% compared with controls using standard aeration, with gains in plant height and leaf length as well Ebina et al., 2013.

In recirculating NFT systems, oxygen nanobubbles were associated with a 126.5% increase in root length, a figure reported in a review Mamun & Islam, 2025. A larger root system has more surface for nutrient uptake.

In deep flow technique (DFT) culture, microbubbles promoted lettuce growth by increasing uptake of dissolved nutrient ions, across the electrical conductivity (EC) levels tested Park & Kurata, 2009; Foudas et al., 2023.