Yeap, you have to keep up with water changes to keep the nutrients at bay, also that looks like hair algae. You're probably going to have to remove most of that hair algae manually and water your water parameters by doing scheduled water changes and light schedule to slowly fight off the algae.
the lights will be 6 months in july. i use a gravel sand mixture. i do water changes every 4 months. the last water change of 100 gallons was done a few days before this pic.
some set-ups work with rare water changes. But that generally involves tons of live plants. You might be better off with smaller, more frequent water changes, and a thorough scrubbing of the decor. In addition, add some floating plants to suck up nutrients and set your timer for the lights to 6h on, then 2 h off, then 6 h on. Algae don't like the dark period in the middle of the day.
Your tank definitely has nice potential, just wants a bit of elbow grease to kick-start