Black stains are spreading.

[mb61]

This is a salt water pool with a propane heater. Black stains are spreading into the swallow end. Pool guy put muriatic acid in the pool, didn’t help. What else can be done. I scrub with a brush and it doesn’t budge?

 

[JohnT]

Welcome to TFP!

Have you ever used an algaecide or alternative sanitizer that contains copper?

Having your water tested for copper would be a good first step.

 

[JoyfulNoise]

We need to know a lot more about your pool with pictures and descriptions of the equipment, how you take care of your pool and how you are testing your water. There’s too little information to give any decent advice.

 

[JamesW]

Looks like it is probably copper.

Drop a vitamin C tablet on a spot.

Can you show your system?

Can you post a full set of chemistry readings?

 

[JamesW]

Can you show the original color of the pool?

Can you remove the cartridge from the filter and show what it looks like?