Algae ID

[Beverly]

Baking soda will lower pH. Washing soda will raise pH.

The Reef Chemistry Calculator to help determine how much to add:

http://home.comcast.net/~jdieck1/chem_calc3.html

Aquarium System Volume Calculator to better determine the actual water volume in your system:

http://home.comcast.net/~jdieck1/volcalc.html

As well as...

High pH: Causes and Cures:

http://reefkeeping.com/issues/2005-03/rhf/index.htm

Low pH: Causes and Cures:

http://www.reefkeeping.com/issues/2004-09/rhf/index.htm

Dominik,

That macroalgae almost looks like some kind of caulerpa, especially if it is invasive.