Good morning Tree. If your tank has been running for less than six months, then you're likely dealing with a form of algae. If your tank isn't well planted, then I'd start there, by adding some fast growing stem plants. When I had an algae problem, I planted Water Sprite, Water Wisteria, Rotala, Ludwigia and Pennywort. As the stem plants grow and draw more nutrients from the water, the algae will die back. No need for lighting changes, feeding changes, plant scrubbing or chemicals, but increase your water changes to 50 percent every two to three weeks if you're not already doing this.
I've used this plant and water change method and have had no algae problems.