Brown diatom algae affect both freshwater and saltwater aquariums. Single-celled organisms, brown algae are nearly microscopic plants. They're not harmful to your fish, but they can quickly make your aquarium appear dirty. Often seen before beneficial organisms are balanced in newly set-up tanks, brown algae can be an indicator of poor water quality in established aquariums.
Limit Light Levels
Brown algae require light for growth, and the more light they receive, the faster they grow. Cover windows and glass doors with blinds or heavy drapes to control ambient light if your aquarium must be placed near them. Fish require at least six hours of consistently timed light daily. Turn your aquarium lights on for 6 hours to 10 hours, at the same time each day.
Limit Required Nutrients
Diatom algae needs nitrogen, phosphorous, potassium and silicate to grow. Feces, uneaten food and rotting plant debris contribute to these nutrients. High levels of phosphorous and silicates are often found in tap water. Perform water changes regularly, siphoning from your aquarium's floor. Feed quality food having a low-phosphate content, and avoid over-feeding. Don't crowd your tank with too many fish, and remove dead fish immediately. Test your tap water for phosphates and silicates. For elevated levels, use reverse osmosis water, an external phosphate-removal filter or a diatom filter.
Use Live Coral and Plants
Densely planted freshwater aquariums and saltwater tanks having live coral are less likely to experience brown algae blooms. Living plants and coral are both photosynthetic, and they compete for the light and nutrients required by diatom algae, helping to create an unwelcoming environment for algae growth.
Add a Few Algae-Eating Animals
Some fish, including blennies, parrotfish and tangs, will eat algae, but they typically don't consume enough to make a difference. Crabs, sea urchins and snails will eat plenty of algae, but most saltwater fish consider them prey. Keep them in aquariums having only smaller fish. Also, some snail species repopulate so rapidly they become a nuisance. A small plecostamus or two can be beneficial.; supplement their diets with algae wafers for proper nutrition.
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