algae on sand bed only

I have an established mixed reef that has been going strong for about a year and suddenly I had an algae outbreak on my sand bed. It is weird because it does not cover the whole sand bed, mostly the corners and by the rock. It is a light green color and it makes the sand clumpy. I have tried covering it up and within a few hours it will reappear. I have no other algae issues (glass, rock, etc.) All the levels in my tank have not changed. Has anyone had this problem before?

My tank is a 20g, light- 4 X 24 watt T5 HO 1000k and actinic, fish-clown and coral beauty, sea star, and some hermits, all corals are doing well.

 

Ro/DI water?

 

of course

 

well have you done anything different with your light schedule?

 

well i read your other thread so im assuming it's the new light. any change like that is bound to create algae, especially if there hasn't been algae for a long time

 

The algae outbreak was before I added the new light and since the new light it hasn't gotten any worse or better. its the strangest thing

 

ok thats just awkward... well maybe your old light might''ve been failing a bit; thats the only real explanation i can think of

 

IME newer lights do not tend to cause algae blooms. Prehaps consider changing out any carbon you have or adding some carbon with GFO if you have not already. Also you may want to play with the flow patterns in the tank.

 

can we see a pic. it might be green cyno