Well I started to Google this problem a little further. I have come up with possible causes called dinoflagettes. Here is a good write up i found online
You could have one of two things growing in your tank. First of all it could be a form of cyanobacteria. This usually comes in a red form in most saltwater tanks but can also be green or brown. When disturbed this "algae" will come off in tissue paper like pieces and can be slimy in texture with trapped oxygen bubbles in it. Cyanobacteria bloom in tanks that have a high dissolved organic nutrient in the water. Aggressive protein skimming, the use of activated carbon and more frequent partial water changes using only reverse osmosis or distilled water to mix with your sea salt can help control its growth. Raising the alkalinity with buffers or calcium reactor and using kalkwasser for top offs will also help. You could also have a bloom of dinoflagellates. This is less common than cyanobacteria but can form in tanks that are new or biologically unstable. It is almost always brown in color, slimy with trapped air bubbles and comes of as powdery pieces when disturbed. In a newly set up tank the best course of action to take is to simply raise the pH(to 8.4-8.5)with kalkwasser, lower the amount of time the lights are on(if possible), manually removing as much of the algae as possible every day and keeping the nutrient levels low. It can last for months and be very difficult to get rid of and is an indication of a high nutrient load in the water. It is very difficult to tell these two apart but a good indication of a dinoflagellate problem is the rapid loss of snails in the system. Snails are effected very badly by the toxin that dinoflagellates produce and very good indicators of this problem algae. Most people do not want to hear that they are having a water quality issue but if you have any undesirable algae blooming in your tank and especially if it seems like a cause for concern then there is a water quality issue going on. All algae have certain nutrients that they need to thrive. Most of these nutrients are wastes products of the natural processes going on with the inhabitants of the tank. Simply testing your water does not give any indication of what may or may not be wrong. Algae utilize ammonia, nitrite, nitrate, phosphate and various other components typically found in a tank. When you measure these variables in your water you may get a reading of zero and think there is nothing wrong with your water. But the fact remains that if algae are growing then there is a high enough concentration of these nutrients in the water to promote their growth and the water you are testing is not showing evidence of this due to the fact that the algae are taking up these nutrients to use for their own growth. Essentially you are testing your water after the algae have taken the compounds out of the water column and they are what is keeping your levels in a healthy zone. Does this make any sense?
