Originally Posted by alphaque

Hi

All the while, my reef marine tank (3 feet) is OK except there are some algae stick on the glasses after 2 weeks of change, i treat that is normal

But started one month ago, i notice there are one layer of dirty thing appear on the surface of the water after 1 week of water change. The algae like surface is not oily and it started with a small "dirty" thing on the surface and when time goes by, it will become thicker and thicker and cover the whole surface until my 4 T5 FL lights cannot penetrate the water and the coral cannot grow. I also notice at the edge of the water surface, there are some greeny things begin to stick on it (pls refer to 3.jpg attached)

Even i changed the 2/3 of the water, i still can't get rid of that dirty surface. it will come back after a week

I asked the marine shop, they said it was caused by the excess phosphates and silicates so i used Seachem PhosGuard™ Filter Media but it still the same result, no improvement at all.

Can any sifu tell me what caused this irritating dirty surface ? Is it i didn't put enough trace elements or some other reasons ?

Pls help me here, thanks in advance...