Not only that, how long do you leave your lights on? How often do you feed? Do you have any sort of cleaners? Did you test for nitrates or phosphates? all of this stuff can cause algea to grow.
No direct sunlight. I have a crab and 2 nassaries snails. Sorry if the spelling is wrong. All the levels are normal. I feed frozen shrimp every other day. I leave the lights on for about 12 hours per day.