Slime Algae

Other Names: Blue-Green algae, Smear algae

Color: Blue-green, may also be brown or black.

Appearance
Very slimy, when disturbed comes off in sheets. Grows quickly and covers all surfaces in the aquarium, often giving off an unpleasant swampy or fishy odor.

Cause

• Cyanobacteria
  
• High levels of organic wastes
  
• Anaerobic conditions

Also referred to as slime or smear algae, blue-green algae is actually the organism cyanobacteria. Overgrowth of this organism generally occurs when there are high levels of dissolved wastes and nutrients in the water.

This may be due to lack of water changes and regular maintenance, overfeeding, or because the tank is new and the beneficial bacterial colonies have not become established. However, because cyanobacteria can fix it's own nitrogen, it can appear even in a well maintained matured tank.

Cure

• Physical removal
  
• Clean tank well
  
• Partial water change
  
• 200 mg erythromycin phosphate/10 gallons water

Once established, blue-green algae is difficult to eradicate. It can initially be removed by scraping the glass, scrubbing gravel and plants, and vacuuming the substrate. However, the algae will soon return, especially if the underlying causes are not corrected. Regular ongoing water changes and maintenance will delay and sometimes eliminate reoccurrence.

Treatment with erythromycin will eliminate the bacteria causing the slime. However, use of erythromycin can also affect the beneficial bacteria in the aquarium, and should be used with care. If such treatment is used, monitor ammonia and nitrite levels closely for several weeks.

Note: Algae eaters do not eat cyanobacteria.

Prevention

• Regular water changes
  
• Regular aquarium cleaning
  
• Avoid overfeeding fish

As with any algae, keeping the tank clean and performing regular water changes is one of the best preventative measures. Unfortunately it is still possible to get algae in spite of regular maintenance. In fact, small amounts of algae is normal. Prompt attention to sudden algae growth will prevent more serious problems.