Brown algae everywhere

I have had my 75 g tank up for 5 months. I don't know how often I should do water changes I have probably done 3 water changes about 10 gallons each time. I use the spring water that gets delivered on the Deer Park truck for my top offs. I now have brown algae all over the rocks and sand. How do I get rid of this and what should my regular water change schedule be?

 

Water change schedules differ from tank to tank.Some people do them often but there are some members here who hardly ever change the water. Alot has to do with bioload and or the number of corals you have plus the filtration employed. I personally do a 10 gallon WC once a week on my 90. The brown algae could be diatoms. It if looks like grains of salt this is probably what you are experiencing. A picture will help I.D. it.8)

 

Have you tested your water. You should be using RO/DI water, as far as water changes go some people do once a week and some do once a month and some do none at all. It all depends on ones tank.

 

+1 to both

There's no way to test for all the impurities that can be found in tap or even bottled spring water, some of which can build up over time and become lethal to your pets. If you're experiencing diatom blooms, you're most likely importing silicates through your water source.