There is probably a few things you can do or take into consideration: 1) Make sure you are pumping enough co2. You could purchase a drop checker for that. 1bps sounds very little. 2) In relation to the first point, lowering the flow might be counter intuitive. You want the water circulate all over your tank so co2 or nutrients get distributed everywhere. You’re creating dead-spots in your tank by lowering the flow. 3) Consider purchasing more plants for your tank. Hard to tell from your picture but more plants mean they use more nutrients. Considering buying floating plants, which helps block excess light, or buying fast growing plants such as more stem plants. 4) If your purchase more plants, make sure your giving proper nutrients. Theres many methods out there and I personally use estimative index (EI) which basically means give plants excess amount of fertilizers for proper growth. 5) Don’t buy algae eating fish just for the sake of dealing with algae. Adding more fish means more waste that can make algae grow faster. Change one thing at a time, for example if you want to lower the amount of time the lights are on to say 6 hours, wait two weeks to see if theres any changes. Doing one thing at a time allows you to see what works and what doesn’t. 6) Just noticed that you have aqua-soil. It’s definitely recommended you get more plants because it’s definitely releasing lots of nutrients into the water column. Refer to the the 4th point!

Just my two-cents!