NEW Pool Owner batteling Mustard Algae

Apr 20, 2018
Ft Lauderdale, FL
Hi everyone!
First of this site is amazing! You guys are so on point. I've been researching things on my own after the pool store couldn't help anymore. I came across the CYA/CHLOR chart and was amazed. Read a few threads and just like it said after i shocked the pool and chlorine levels returned to normal algae appeared again. I read the thread about mustard algae and purchased the test kit you guys recommended.
I ran all the tests: FC 8, CC 1, PH 7.5, CH 750, Cya 70.
Im looking to do the mustard SLAM levels but should i lower my CYA with a partial drain and fill?
Any comments or experience is greatly appreciated.


TFP Expert
LifeTime Supporter
In The Industry
Jun 12, 2009
NW Ohio
Welcome to TFP! Let me congratulate you right off the bat on the test kit, good data to base your pool care off of is one of the most important things you need to really take control.

Firstly, mustard level is not what you SLAM at. You perform a SLAM normally and then after you complete the SLAM you follow the Mustard Algae procedure.

More importantly though, what are you basing your mustard algae diagnosis on? It sounds like you just shocked the pool and algae came back, if that is the case it is possible that the algae just wasn't finished off and came back when the FC dropped back down. Your CC of 1 points in that direction as well. I would just start with a and see that to completion. I'm betting the algae won't come back as long as you keep your FC in check with your CYA.

With your CYA and CH both high then a partial water change will help both of those. The CYA isn't that big a deal, 70 is manageable, but bringing it down won't hurt and you really want to get your CH down.

Sounds like you are getting on the right track. Best of luck with everything!