Experimental design
Plastic aquaria were chosen due to the low Cr adsorption of such material. Aquaria were placed outdoors under a plastic sliding roof. During the experimental period the average ambient temperature was 22C (max 24C, min 14C). Water pH was slightly acidic during the experiments (5.4–6.0). Aerators were placed in the aquaria to maintain aerobic conditions
during the experiments. Lake water was added daily, to compensate for water losses through plant transpiration,sampling and evaporation.Each experiment was repeated in duplicate runs.