These results illustrate that the crop chosen can have a considerable impact on the removal of nutrients. Nasturtium removed nutrients faster, removed both TAN and nitrate, and reduced effluent nutrient concentrations to a greater degree. Faster removal, i.e. an increased uptake rate, indicates that a shorter retention time is necessary to achieve the same final concentration than would be required if a crop such as lettuce with slower removal is grown .If a crop with a relatively high removal rate is grown in a system designed for crops with lower removal rates, plants, especially those especially those at the end of the channel, will probably be nutrient limited and grow at a slower rate, reducing crop yield. This problem can be reduced by decreasing plant density or by not planting the entire channel. A second factor to consider is the minimum concentration realistically attainable by the potential crop. In both crops there wasa minimum concentration to which crops could remove nutrients,and when the concentration approached this minimum, little additional uptake occurred. Increased retention time, either through the use of longer channels or a slower influent velocity would only decrease plant growth without additional removal.