Pool water clear but algae on sides

[SALTPOOL]

Just got back from vacation. the pool walls had some algae on them but the water is clean. i have a basic test kit and here are my numbers,.

tc 3
fc 3
cya 80
ph 7.5
alkilinity 70
ch 110
salt 3400

31000 gallon pool 18 by 36 with 4 foot roman ends on each side. mod media filter, swg, no water falls or deck jets vynyl liner..
why would i be getting algae on the sides.??

 

[jblizzle]

Welcome to TFP!!!

why would i be getting algae on the sides.??

Easy, because your FC got too low.
According to Pool School in This Chart, the MINIMUM the FC should be with a SWG and a CYA at 80ppm, is a FC of 4ppm.

You need to SLAM the pool. [slam:1rk72ybh][/slam:1rk72ybh]

This is done with the SWG off and you WILL need one of the Recommended Test Kits.