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    Illustration of green water

    Fish mortality

    Understanding the causes of mortality
    and restoring a vital balance

    fish mortality 1 1

    What you see

    The situation is critical and often changes very quickly:

    • Fish are found dead on the surface or on the bottom, sometimes in large numbers within a few hours. The carcasses may show no visible signs of injury.
    • The surviving fish crowd at the surface, mouths wide open, desperately trying to gulp in oxygen from the air.
    • Severe lethargy (the fish do not scatter), erratic swimming on their sides, or gathering at the water inlets.
    • Very pale gills or, conversely, bright red gills; exophthalmos (bulging eyes); or localized skin redness.

    What this means

    In 90% of summer cases, the cause is not a viral disease, but a decline in water quality. The diagnosis generally points to two main scenarios:

    1. Acute Anoxia (Lack of Oxygen): This is the most frequent cause in summer. The water temperature rises, the solubility of oxygen drops, and the nocturnal respiration of algae or mud consumes the little remaining reserve. The oxygen level drops below the "lethal threshold" (often < 3 mg/L) in the early morning.
    2. Ammonia Poisoning: This is the invisible killer. If the pH of your water exceeds 8.5 (often in the afternoon), ammonium (slightly toxic) chemically transforms into Ammonia (NH₃), a devastating neurotoxic gas. This often happens after a storm or a failure of biological filtration.
    fish mortality 2 1

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    Why act now?

    Death may occur within a few hours.

    Decaying fish exacerbate the crisis, releasing ammonia and pathogenic bacteria, and further destabilizing the environment.

    Activities (fishing, recreation) become impossible, and the remaining wildlife is at risk.
    A mass die-off is almost always a sign of an overburdened ecosystem on the verge of collapse.

    The TASO Solution
    Emergency oxygenation & stabilization

    When fish die, a quick response is critical.
    Our goal is to restore oxygen levels and stabilize water chemistry.

    1

    Backup oxygenation (mechanical action)

    The top priority is to oxygenate the water. We install OXYLAKE aerators to stop suffocation immediately.

    The action produces: They inject air deep down and cause a mechanical "degassing" that expels volatile toxins (Ammonia) into the atmosphere.

    2

    Mineral stabilization

    To stop the contamination, the water chemistry must be stabilized. We apply NAUTEX (pure calcium carbonate).

    The action produces: It raises the buffering power (TAC) to lock the pH. This prevents ammonium from turning into deadly ammonia gas. It is the chemical antidote of the medium.

    3

    Reduction of organic load

    A fish kill causes massive organic pollution (dead fish, slime).

    The action produces: We inoculate the bacteria Biolimpid to rapidly digest these wastes, thus avoiding a second wave of mortality due to water pollution.

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    Products
    & Related Solutions

    nautex

    Nautex

    the standard mineral treatment for all bodies of water
    Learn more
    oxylake

    Oxylake

    Oxygenation solutions for ponds and bodies of water
    Learn more
    AQUASUB

    AQUASUB

    The intensive mixing hydro-ejector
    Learn more

    Need a study?

    Each protocol is tailored to the initial assessment, the characteristics of the body of water, and its intended uses.

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