Other control measures
Algaecides
In freshwater systems (without plants) we can apply algaecides to help keep the algae production under control. This option also exists in Fish Only saltwater tanks, by using a low level of copper (0.010 PPM). But for saltwater aquariums with fish and invertebrates or corals, copper is NOT an option and can be toxic to the invertebrates and coral. It is also toxic to some fish.
Controlled cultivation
If there are plenty of corals and the like to compete, it is possible to cultivate green algae in areas of the aquarium where it does not annoy us. This will limit the growth of algae in areas where we do not want it.
More on slime algae
Nuisance slime algae is a problem in saltwater aquariums, particularly with new tanks where conditions will vary more than in a mature system. Usually the brown style is the first algae to appear, followed by a green slime. These are a Cyanobacter species of bacteria, not true algae, so lighting is of little importance. Sudden appearances in a well-established aquarium could be related to a decrease in metabolism in the competing organism caused by a decrease in intensity of older lights. Once again, replace the bulbs.
Even with our best efforts, sometimes the slime Cyanobacter will appear to take over. In that event, it is best to turn off your pumps, gently wipe the slime off the glass, gravel and rocks, and let it settle and siphon it out of the aquarium. There are "slime" treatments that will "kill" the Cyanobacter (active ingredient is erythromycin), and in some cases they will eliminate the slime. Remove the excess slime before treatment, and make sure the nitrate and phosphate levels are as low as possible.
Hair algae
Perhaps one of the other great scourges is hair algae. While nutrient control is still essential, in the saltwater aquarium we can utilize Scarlet Leg and Blue Leg Hermit Crabs to eat the offending algae. Also, if the calcium levels are maintained above 350 PPM, the coralline algae will compete for attachment sites. In freshwater aquariums, some success has been reported using Glass (Ghost) Shrimp to control hair algae. If you develop "brush" or "beard" algae on the leaves in your freshwater aquarium, the best method of control is to prune the affected leaves before it spreads. It has been reported that higher levels of CO2 will help control these algae, perhaps by making the true plants healthier and less likely to allow attachment of the algae to their leaves. When all is said and done, prevention is the best method of control.
