May want to reevaluate your filtration setup and/or water change (WC) schedule. Replacing the GAC enough (if using) ? Replacing filter pads? Skimmer ? May want to consider an algae scrubber, algae reactor, refugium.
Concerning WC for me the best way to know if you're doing too little or too much water changes is the nitrate levels. Concerning Algae issues, then also test for Phosphate. Overall ppl agree 0.2 ppm or below for Phosphate. Nitrate ppl say under 20 ppm. You will want to test, I use Red Sea Marine Basic. Phosphate I use Hanna but is on expensive side ~$50.
Reducing over the top Phosphate levels may require chemical, such as Phosphate-E from Brightwell. Nitrate can also do carbon dosing, or WC. There are articles out there for carbon dosing; if considering will need to research; idea is if you add vodka to tank it eats nitrates away, that is basics (haven't tried it).
Sometimes when you have algae issues you may also have a bacterial imbalance. I highly suggest Brightwell Aquatics mb7 (bulkreefsupply.com) to help resolve this. I sense the tank has this imbalance also with WC and possible filtration issue; bacterial load is usually an issue when a tank is somewhat new. Algae, cyano, diatoms, dinos (bad ones) are all things that grow easily and will battle the good bacteria. Bacterial continues spreading and dying until all find a balance; dying which release penicillin and more nutrients into water causing another race for territory, the mb7 has good bacteria to help remove this new tank syndrome.
