Golden alga density can become problematic at 10,000 cells/ milliliter of water but typically in Texas we see large scale fish kills with densities of 20,000 cells/ milliliter. If golden alga is found in your pond it will be important to conduct cell counts via microscope periodically from December – April each year to determine when golden alga densities become too high. Water quality can greatly affect the likelihood of golden alga blooms so it is also important to monitor salinity, temperature, and pH throughout winter months.
To reduce the likelihood of a golden alga bloom it would be best if at all possible to first pump water from alternate sources which are lower in salinity. If no alternate sources are available then always pump water from the deepest location possible. Water 20-30 ft deep should be less likely to have a high golden alga population. Pond dyes may be useful in reducing plankton density because they shade the water column. However, pond dyes also greatly reduce the beneficial plankton which will decrease the productivity of the forage chain.
To prevent fish kills it would be advised to monitor golden alga cell counts in the water and any time golden alga begins to dominate the algae population an algaecide should be applied. Use of algaecides: Copper sulfate .2 mg/L when temperature is below 60 F or Hydrogen peroxide at 3,125 mg/L.
There are is no 100% way to prevent golden alga kills once they are in a pond. The process has to involve monitoring plankton diversity and water quality, reducing salinity and pH, possibly using pond dyes and aeration, and eventually using an algaecide.
By: Steven Bardin M.S.