Bad Hair Algae

[Myka]

Hydrometers are notoriously inaccurate. You should calibrate your hydrometer as it is very likely that it is not reading right. Mine reads 0.002 lower than what the salinity actually is. Now that I know this, I am able to keep my tank's salinity where I actually want it! I keep my tank at 1.026. Your tank at 1.021 is very low. I would suggest raising it up to 1.026 which is the average salinity of the world's oceans that our critters come from, and also the most common level aquarists keep theirs at.

Here is a link to calibrate your hydrometer: http://reefkeeping.com/issues/2004-06/rhf/index.php