Algae?

[Marinemammalover]

My tank has been cycled for about two months and this stuff has been appearing on some of my airline tubing..... It has black spots on it and I was just wondering what it is? Is it algae?

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[rotorhead22]

Could be black algae. What are your nitrate levels? Algae will thrive with high nitrates. Try to keep nitrates below 25 ppm.

 

[Marinemammalover]

My nitrates are around twenty, ph is 7.6 and everything else is zero.... Is black algae dangerous? I just did a 25% water change... It's a cycled twenty gallon tank with five zebra danios, a power and a sponge filter... Any advice would be great... Thanks!

 

[Cichlid Kid]

Looks like diatoms to me.
Diatoms are common in newly setup aquariums and although not visually appealing, they pose no real danger to livestock. Frequently cleaning decor "and in your case airline tubing" will help. As the tank matures they'll eventually go away.