Hi all.. I'm back again. With the same issue. We believe we have mustard algae and we are not getting rid of it. We've also changed out the sand in our filter so I know that's working good :-) But my water is now green cloudy mess and I have nasty brown deposits on the bottom that my husband can't seem to get rid of.

So... I need to nip this in the bud once and for all... Here are my numbers



FC: 5.5
CC: 0
PH: 7.2
ALK: 70
CYA: 25 (reading stops at 30 but I still had to add more to bottle to see black dot disappear

Please help !!