Saltwater aquarium keepers often encounter the pesky issue of red slime, also known as cyanobacteria. This guide aims to provide comprehensive strategies to maintain a healthy, vibrant aquarium ecosystem by effectively combating and preventing the proliferation of this unsightly bacterial growth.

Understanding Cyanobacteria

Cyanobacteria, or red slime, is a type of photosynthetic bacteria that appears as a slimy, colorful coating in aquariums. It primarily presents in shades of deep red or purple but can also appear green or black. It will blanket the sand bed, rocks, corals, and even equipment. Thankfully, it's easy to remove because it lacks roots or any strong attachment to the surfaces it coats. 

It's important to note that it is not an algae but a bacteria, often misleadingly referred to as "Red Slime Algae". While it isn't directly harmful or toxic, it can suffocate corals and other marine life by blocking light, essential for their nutrition and growth.

Causes of Cyanobacteria in Aquariums

The exact causes of cyanobacteria can vary, but it's often attributed to:

  • Nutrient Levels: Both high and low levels of nitrate and phosphate can contribute to the growth of red slime.
  • Water Flow: Areas of minimal water flow in the aquarium, like the sand bed, are common starting points for cyanobacteria growth.

Effective Strategies to Combat Red Slime

1. Increase Water Flow

Enhancing water circulation in the aquarium can dislodge the loosely attached bacteria, making it easier to filter out. Strong water flow prevents the cyanobacteria from settling and proliferating on surfaces.

2. Manual Removal

Regular manual removal is crucial:

  • Targeted Blasting: Use a turkey baster to gently blow the cyanobacteria off rocks and other surfaces so that it can be removed by filtration.
  • Siphoning: Regularly siphon off larger blankets of cyanobacteria, ideally running the water through a filter sock to trap the dislodged material or in conjunction with your regularly scheduled water change.

3. Cultivate Beneficial Bacteria

Incorporate beneficial bacteria supplements, such as Microbacter7, into your aquarium. These beneficial bacteria can out-compete cyanobacteria for resources, significantly reducing its presence.

4. Consider Chemical Solutions

For persistent cyanobacteria, a chemical solution like Chemi-Clean can be used as a last resort. However, it's crucial to continue physical removal even after treatment to prevent recurrence. Chemi-Clean is reef safe, but can lower oxygen levels within the aquarium, so be sure to read and follow the dosing instructions.