Is Cyanobacteria dangerous or harmful to fish?

It's known to be an issue for some animals (specifically, those who may drink or eat it directly or indirectly), but it's not really known to be an issue when it comes to harming fish - but it will cover your plants if you have any in the tank and kill them off completely (by preventing them from being able to capture any light from its leaves).

It's highly recommended to remove it either through a natural treatment (for example; getting more powerheads or water movement where it seems to be more centered on/at), or use an algae treatment to remove it from the tank.

Yo, JustAFishServant here!

So, I saw Leon's post about cyanobacteria in his tank. Lemme break it down for ya, folks. Cyanobacteria can be a pain in the butt, but luckily it's not really harmful to fish. But hey, it can wreak havoc on those precious plants of yours. If you let it go wild, it's gonna mess with their light intake and kill 'em off. Not cool, right?

My advice? Don't just chill and leave it be. You gotta take action, my friend! Either amp up the water movement in the affected areas or grab some algae treatment to get rid of that pesky cyanobacteria.

Keep those tanks clean and happy, peeps! No room for unwelcome visitors like cyanobacteria. Stay vigilant!

Peace out!

Cyanobacteria, often referred to as blue-green algae, can indeed present several issues in an aquarium setting. While it is generally not directly harmful to fish, it can create an unhealthy environment indirectly. Its rapid proliferation can lead to several problematic conditions:

1. Oxygen Depletion: Cyanobacteria can consume significant amounts of oxygen, particularly during the night when photosynthesis ceases. This can stress your fish, especially in a tank with an already low dissolved oxygen level.

2. Light Blocking: As noted by other members, cyanobacteria can cover plants and substrates, obstructing light penetration and thereby hindering photosynthesis. This can ultimately lead to the decline and potential death of aquatic plants, disrupting the ecological balance of your aquarium.

3. Toxin Production: Some strains of cyanobacteria produce toxins (cyanotoxins), which can be harmful to both fish and other aquatic organisms if present in high concentrations.

4. Aesthetic and Practical Issues: On a more practical note, cyanobacteria can be unsightly and produce unpleasant odors. Its slimy texture can also clog filters and other equipment, leading to maintenance challenges.

To mitigate cyanobacteria growth, consider the following steps:

• Increase Water Flow: Enhanced water movement can prevent cyanobacteria from establishing on surfaces.
• Nutrient Control: Reduce excess nutrients, particularly phosphate and nitrate, through regular water changes and controlled feeding.
• Lighting Adjustment: Limit the amount of light your tank receives, as excessive light can promote cyanobacteria growth.
• Manual Removal: Physically remove cyanobacteria from surfaces during routine maintenance.

Addressing cyanobacteria proactively will help maintain a healthy and balanced aquarium ecosystem.