Moderate blooms of phytoplankton are desirable, but these are hard to maintain with the high feeding rates in fish culture today. To date there is no effective way to manage a phytoplankton bloom other than reducing nutrient input in the form of feeds. Other methods have been used to try to control phytoplankton densities but have been completely ineffective. Thinning the phytoplankton bloom in this manner results in very poor water quality and overall reduced fish production. The use of dyes to shade out dense phytoplankton blooms has been studied.
Dyes probably result in poorer water quality throughout the growing season.
Dyes may also select for undesirable blue-green algae in treated ponds. Phytoplankton Die-Offs Phytoplankton density tends to increase steadily through the growing season. Communities in individual ponds, however, often exhibit a marked periodicity in concentrations. It is not uncommon for phytoplankton communities to crash even with high nitrogen and phosphorus concentrations. Certain species of blue-green algae are known for their sudden crashes.