TGP and GBD: The invisible imbalance
Gas bubble disease (GBD) develops long before external signs are visible, and it begins with elevated total gas pressure (TGP).
When TGP exceeds local barometric pressure, water becomes supersaturated. Oxygen values may appear stable, yet nitrogen-driven imbalance can already be present. In shallow tanks and RAS systems, fish cannot compensate by moving deeper. If exposure persists, dissolved gases form emboli in tissues and blood vessels.
By the time eye bubbles or behavioral changes appear, the imbalance may have existed for days.
The critical question is not whether GBD is recognized. It is whether TGP is routinely controlled as a production parameter.
Supersaturation is typically mechanical in origin: air entrainment at pump suction, oxygen injection under pressure, limited degassing capacity or hydraulic restrictions. These are system dynamics, and therefore manageable.
Measured at intake, after pumping and oxygenation, the pattern reveals where gas is entering or failing to escape. Adjustments can then be made where they matter most: air leaks, injection pressure, degassing efficiency and excess head pressure.
Without measurement, any imbalance is only recognised after symptoms appear. With measurement, you can control the gas balance.
Read more about TGP and GBD, including a detailed technical article explaining exposure dynamics, risk thresholds and practical mitigation strategies across hatchery, RAS and grow-out systems, on the OxyGuard website.
TGP and GBD: The invisible imbalance OxyGuard ®
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