Looks like what I have ..... been trying to get rid of it for months .....
This may be black beard algae, or maybe some form of diatoms or blue green algae .... a close up might help, but true ID
needs a microscope (& a biologist
BBA is tough to get rid of, nothing will eat it (although some will as a last resort). I did lots of looking on the net (& the plant forum here) & eventually settled on correcting a presumed nutrient imbalance by adding KNO3 to the tank. This is supposed to work only in high light planted tank with CO2
gives the plants a boost so they can outcompete the algae).
I've had some success with this in my low light, no CO2
planted tank. I kept the NO3
level around 10 by adding 1/2 teaspoon of KNO3 a week. The BBA isn't all gone, but is not coming back after I physically removed it.
Last week, however, possibly because my hornwort had grown so much & taking in more nitrates than before, the NO3
level fell to trace .... and the BBA was back within a couple days ... so I am back to increasing the KNO3 dose & cleaning everything ... AGAIN ........