These things can actually filter out parasites which a good thing in the short term, but can make your fishes immune system 'lazy'. Also, it will filter out good bacteria as well as bad.Originally posted by F.sparverius
Is there any great harm in letting one of these things run nonstop. Also would it eliminate brown algea. I seem to be getting quite a bit of the stuff lately.
I only use the filter to 'polish' my water from time to time. There are naturally occurring oganisms that will control algae. It takes a few months before these become properly established in a tank.