Hi, I've had my 20 gal tank for over a year and although I've had algae many times in my tank, I've never had brown algae before. I use to have gravel rocks in my tank but then went barebottom for a while since I always worried that my fish would choke. I decided a couple of weeks ago to put gravel substrate in my tank because they were smaller and it looks more natural in the tank since the gravel is sand color and now there is brown algae. I read in one of the posts at the top that phosphate levels can cause brown algae, that is why I am wondering if gravel substrate can affect phosphate levels?

I've never been able to lower my nitrates, my nitrates always seem to be between 30 and 40, but they've never caused brown algae before. My fish appear fine, very active, always hungry, etc.


thanks

karla