Blue-green algae, SLAM, passed OCTL, now scaling - what to do next?


New member
May 23, 2018
First time posting; but a long-time follower of TFP. A new pool owner five years ago and I went the pool store route for two years and was “pool-stored” for sure. Then I found TFP! The info here is invaluable and has kept my pool in great shape the last three years! Not sure what went wrong with closing last year; but we opened the pool to an extensive green – blue algae problem which required a two-week SLAM to get rid of. Just this morning passed all three SLAM criteria: CC is .4, OCLT loss .2 and the water is clear. About half way through the SLAM started seeing scaling. We continued with the SLAM, based on forum comments which said to get through a successful SLAM and then address the scaling. The diluted muriatic acid test on the scaling fizzled which indicates it is Calcium Carbonate. I’d appreciate your recommendations on next steps for dealing with the scaling and the best process for returning the various levels back to recommended. And of course, the most important question from the kids….is it safe for them to swim? BTW…the SWG was turned off during the SLAM and has not been turned back on yet. Thanks!!!
Fill WaterWed 7PMWed 9PMThur
CYADidn’t register any303030
FC 25mL sample.22.410.410.2
CC 25mL sample.
PH 44mL sample7.
TA 25mL sample210200220210
CH 25mL sample210230250220
ADD 10% liquid bleach256oz @9pmNo AddNo Add
Water Temp78


TFP Expert
Platinum Supporter
May 23, 2015
Tucson, AZ
Your TA is very high but if your pH remains stable at 7.4, then your CSI is balanced. If you tracked CSI you’d see that at a pH of 8.0 your water is well within scaling territory due to the high alkalinity. I would suggest that you track CSI regularly because you are using an SWG for chlorination and the cell is much more susceptible to scaling than your pool surface. You should be targeting a slightly negative CSI, so a little less TA than your fill water, to ensure there’s no scaling in the cell.