Brownish stains moving around

jawathehutt

Member
Apr 10, 2023
8
Maryland
Pool Size
25900
Surface
Plaster
Chlorine
Liquid Chlorine
I am experiencing some unusual staining in my plaster pool. There are a bunch of brown spots that seem to be moving around the pool. They do not feel any different from the rest of the pool and occasionally mostly fade away and then reappear a few feet away a few days later. I mainly only use 10% bleach and 20 baume MA. I tried to rub it out with a Puck to no luck so it doesn't seem to be algae.

My FC is generally 3-7, ph generally 7.4-7.8, cya is 35, calcium is 350-400, and alkalinity is 70-90, and their presence doesn't seem to correlate to any specific levels. I've only been maintaining this pool for 2 years and know the last owners used an ionizer and God knows what else but I didn't see it this at all last summer. I'm on city water.
 

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Look like stains from fertilizer or some other granular product.

For grins, rub a few spots with vitamin C tablets.
 
That's what it looks like to my eye...seen a bunch of fertilizer stains. You ever find any of the pellets on the deck? You'd have to catch them before a rainstorm...most fertilizers these days are AMS or Urea based and dissolve quickly.
 
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