Ammonia

Definition

Ammonia (NH3 / NH4+) is the primary nitrogenous waste excreted by fish gills and produced by uneaten food + decaying organics. Highly toxic at any detectable level - even 0.25 ppm causes gill damage and stress.

Practical use

Test weekly; target is 0 ppm. If detected, do an immediate 25-50% water change, reduce feeding, check filter media. Common cause: new tank without an established cycle, or filter media replaced too aggressively.

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