Hello, I am new to this hobby. I have a 13.5 gallon tank that I've had set up for about 3 months. It keeps getting this smelly brown algea looking stuff all over my rock and sand bed. I use tap water with tap water conditioner. My ph is kind of low but I'm not sure how to raise it or if that's what's causing the brown stuff. I clean it out and it seems to be back by the next day. I attached a picture. It doesnt show it on this picture but its everywhere! Any help would be appreciated!