I do a 15 gallon water change every three to four months, I donââ"šÂ¬Ã¢"žÂ¢t use a skimmer.
I just did a little experiment, I went over four years without changing the mud. I had xenia that was only a few polyps on a couple rocks. That when I first set up the tank was out of control all over the place. After the three year mark algae was slow growing in the refugium, the xenia didnââ"šÂ¬Ã¢"žÂ¢t spread anymore and looked thin. I changed half the mud and the sump is now full of algae and the xenia is thick and spreading. I have to say Iââ"šÂ¬Ã¢"žÂ¢m not skeptical about the mud anymore, keep up with mud changes it makes a big difference.