Mustard algae experience

[jhm]

It also likes shade so will hang out in light niches, under removable ladders, etc. which all need to be checked.

Nail on the head there, those are the spots I'm talking about. So, maybe even though it is totally in check while keeping my water at good levels, I need to shock the heck out of it for a while to kill it off completely. Ben is probably right too, it's still living in places that I don't expect it, and will expose itself if I slip up.

Thanks!

[jhm]

One other thought, after a thorough shocking should I replace my cartridges, or can I get away with cleaning them? It ain't cheap to replace them.

[chem geek]

If you've got fairly even flow through your cartridges, the high shock level should be sufficient for killing algae in them. You could always clean the cartridges rather than replacing them. Algae won't like detergent, but it's really the chlorine that kills them.