It looks like Green Beard Algae which is just green colored Black Beard Algae.
How long are you running lights daily? What type of light and bulbs do you have? Is your tank planted? If so are you using CO2 or liquid carbon? What about ferts? What is your nitrate and phosphate levels?
BBA can be spot treated with hydrogen peroxide 3% or liquid carbon but unless the problem causing it isn't fixed it will just come back.
Right now start with running your lights only 6 hours daily.
Thanks for your response! I have been running aquariums for a long time but as of two months ago, it has been my first try at planted tanks so I am still really new to all these issues. I never had an issue with algae in any of my non-planted tanks so any advice you can give me would be great. Everything I learned about planted tanks, I learned via this amazing forum.
-How long are you running lights daily? I was running them for 10 hours daily up until early yesterday morning, I dropped it down to 8 hours after reading that 8 is the minimum.
-What type of light and bulbs do you have? I have 2 t5 bulbs - 2watts per gallon
- Is your tank planted? Yes, I have ozelot sword, Java fern (tied to driftwood), Anubias nana (tied to rock), Red Rubin Sword, Hygrophila corymbosa, and Limnophila aromatica.
-Are you using CO2 or liquid carbon? Co2. I have a 5 gallon tank running at 30 psi at about 3 bubbles per second. My Ph is 7.0 and my KH is 6. I don't have a drop checker at the moment and I don't really have the funds right now to get one (ps4 is on the way!!!) but I found a ph and kh graph and according to that, it says I am right where I should be.
What about ferts? Flourish comprehensive 2x a week and a flourish tab for the swords.
-What is your nitrate and phosphate levels? Nitrate levels were 0 when I last did test, 6 days ago before my last water change. I have to do one today, so if it is any different I will update this. Phosphate levels, I actually don't have a test kit for however they shouldn't be more than .5 because I do have a phosphate and silicate remover bag in my canister.
I really don't think I am over feeding however I am not sure if the feeding is different in planted tanks compared to non-planted. I feed the fish about a quarter of a tab of both frozen brine and frozen veggies every other day.
Some additional info-
I guess I should mention, this tank has only been set up for about 3 months. I cycled it using filter media, gravel and items from my old aquarium that I was upgrading from. The cycle only lasted about a week and a half. After about two weeks, when I was sure everything was stable, I started to add additional fish. about 3 weeks in, I had an outbreak of brown algae. I read that it was normal in newly cycled planted tanks and will go away within a few weeks. After about 3 weeks, it stopped growing back after i scraped it off before water changes. Then almost immediately after the brown algae went away, this green algae started to grow.
I don't know if this is true but I read that fluctuating the co2 could cause issues like this and therefor a while I had a horrible fight with my co2 regulator. I really think it was faulty because I checked every inch of my setup with soapy water and wasn't seeing any holes. I eventually bought a new regulator and the problem went away after that. However, for about a month while I had the old regulator, the co2 was all over the place.
What makes black beard algae green anyway? Just out of curiosity.