Slimy green 'algae' in your fish tank is typically Cyanobacteria, often referred to as blue-green algae, even though it's actually a type of bacteria.
Understanding Cyanobacteria in Aquariums
Despite its common name, Cyanobacteria is not true algae but photosynthetic bacteria. It thrives in aquarium environments, often signaling an imbalance in the tank. It's known for forming distinctive slimy, mat-like growths that can be various shades of green, blue-green, or even black.
Key Characteristics:
- Appearance: Forms sheets or mats that cover surfaces like substrate, decorations, and tank walls. It has a slimy, paint-like texture.
- Smell: Can sometimes have a distinct earthy or musty odor.
- Growth Pattern: As noted in the reference, it can start very subtly and may initially seem like not a big deal. Unfortunately, ignoring this green slime allows it to quickly spread.
Why is it a Problem?
Ignoring Cyanobacteria isn't just an aesthetic issue; it can become a significant problem for your aquarium's health.
According to the reference, this green slime thrives on inaction. Wait a week with no action and you may find yourself in a scary situation, a tank covered in this nasty, smelly slime. Rapid growth can:
- Suffocate plants by covering their leaves.
- Impact the biological filter over time if left unchecked.
- Detract significantly from the appearance of your tank.
- In rare cases, some strains can produce toxins harmful to fish.
Identifying Cyanobacteria vs. Algae
While both can be green, telling them apart is crucial for effective treatment.
| Feature | Cyanobacteria (Slimy Green Slime) | True Algae (e.g., Hair Algae, Green Dust Algae) |
|---|---|---|
| Texture | Slimy, mat-like, easily peeled off | Fuzzy, brittle, powdery, harder to wipe |
| Smell | Often has a musty/earthy smell | Typically no strong smell |
| Growth | Forms sheets/mats, often on substrate | Can be hair-like strands, dust on glass, etc. |
| Composition | Bacteria | Eukaryotic organism |
If the green growth in your tank is slimy and peels off easily in sheets, it is highly likely Cyanobacteria.
Addressing Cyanobacteria
Dealing with Cyanobacteria typically involves a combination of identifying the underlying cause (like excess nutrients, light imbalance, or low flow areas) and targeted treatments, often involving specific aquarium-safe chemicals designed to kill bacteria rather than algae. Manual removal is a good first step, but addressing the root cause is key to preventing its return.
Remember, this green slime wants you to wait. Taking prompt action upon noticing it is the best way to prevent it from becoming a tank-wide issue.
