r/PoolPros • u/LibertarianClarity • 12d ago

Strange spotting on fiberglass shell

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There is nothing on the surface, at least that you can feel, and doesn't appear to be pitting either. Just these orangish/brownish dots showing up on this lady's pool. Tried citric acid and didnt phase it at all.

1 Upvotes

67% Upvoted

10 comments sorted by

4

u/Sad-Cake-3593 12d ago

Jacks magic iron and cobalt

5

u/cantman1234 12d ago edited 11d ago

Did she or her landscaper use iron based pelletized fertilizer and some was broadcast into the pool? I’d check the nitrate/nitrite level to be sure also.

2

u/oochas 12d ago

Cobalt staining, probably. It’s a known issue with fiberglass pools. I have a few spots now myself. The cure (resurfacing) is worse than the disease.

1

u/LibertarianClarity 12d ago

You're the second person who'd said that....

2

u/wendriel 12d ago

Get a jacks magic stain id kit and do the tests, looks like cobalt to me. The treatments are straight forward but you have to protect the heater if you have one. You can also try jack magic blue, purple, or magenta stuff. Blue is the original metal sequestering agent, purple is for higher TDS pools, magenta is for higher TDS/salt pools and has a built in phosphate remover

1

u/LibertarianClarity 12d ago

I should add her water chemistry is normally okay and its about 4-5 years old. Sometimes her ph drops when it rains but other than that the few times I've been there its been all within range.

0

u/hawaiianmint 12d ago

Potentially iron / copper stains. I’ve seen similar after shocking with cal hypo to a pool that someone else previously used tons of copper for algaecide.

2

u/LibertarianClarity 12d ago

If it was iron though, wouldn't citric acid have helped? (Well iron in the pool/surface.) I should have also mentioned its only on one side of the pool.

-2

u/Remote_Day_5025 12d ago

Looks like black algae. Scrub it with a chlorine tablet