Yes, it's designed to raise the water level and increase water movement. It goes on the outside of the overflow on the top left side (side where the sponge goes). It's good to reduce the green algae/scum that can form if there's not enough flow. But if you're using the stock lighting and covers, you'll have the water literally touching the lights and glass. It only works if you don't use a cover and have replaced the lighting. Not worth it in my opinion. I added a filter floss holder and an extra powerhead and I eliminated all the yucky stuff on the surface.That goes in front of the weir that leads to the first chamber but it makes the water level way to high so I don’t use it