Toxicity of Aluminum Hydroxide Complexes in Neutral and Basic Media to Rainbow Trout

Toxic effects of aqueous aluminum complexes in neutral and basic media to rainbow trout fingerlings were investigated under constantly flowing, controlled conditions of concentration, pH, and temperature. Toxicities of various concentrations were highly pH dependent. Dissolved concentrations over 1.5 ppm aluminum caused drastic physiological and behavioral aberrations as well as acute mortality. Toxic effects of suspended aluminum, while they are more noticeable at lower concentrations, are not as concentration dependent as those of dissolved forms. The safe concentration of either dissolved or suspended aluminum is well below 0.5 ppm. Mortalities among test animals ceased almost immediately after aluminum exposures were concluded. Recovery times for fish exposed to the various tests were proportional to the severity of the test conditions and to the length of exposure. Normal growth resumed almost immediately in fish from the less severe tests, and after a period of a few weeks in fish from the more severe tests. After up to four months recovery the average weight of fish surviving both chronically and acutely toxic aluminum concentrations is markedly below the control average.