Stubborn Algae on Pool Bottom

[JPMorgan]

So... I was away for two months and upon my return I am seeing some stubborn algae clinging to several areas in the bottom of the indoor pool. Never had it this bad before (Thanks, pool sub guy!) I have been brushing repeatedly (from the deck with a nylon brush), but it doesn't seem to remove it. I have raised the bromine level to 10 ppm a few times, but this doesn't help either. Will raising the bromine level higher help.... or do I need to get in the pool and try to remove it by hand scrubbing? What the heck is going to get this green stuff out of the pool? It's kind of hard to see from the photos, but there is definitely stubborn algae clinging to the bottom of the pool.

 

[JamesW]

It looks like it might be copper.

Drop a vitamin C tablet on a spot.

 

[JPMorgan]

Does the strength of the tablet matter?Found some cheap vitamin C tablets on Amazon. One is 250 mg strength, the other is 1000 mg. If the tablet removes the stain in one spot, what then?

 

[JamesW]

Any tablets should give a result.

 

[JPMorgan]

I haven't tried a stainless steel wire brush on the stuff yet. Should I give that a try or might that damage the plaster or leave marks? (Still need to pick up the vitamin C tabs to test for copper.)

 

[JPMorgan]

Also.... what should I be looking for when I drop the vitamin C tablet on the green stains?

 

[mknauss]

Also.... what should I be looking for when I drop the vitamin C tablet on the green stains?

Iron stain will disappear pretty quickly normally. If the stain changes color, could be copper or silver.

 

[JPMorgan]

Update: looks like a stainless steel algae brush is getting the green stuff up.... slowly, but surely. The nylon brush just wasn't doing the trick.

 

[JPMorgan]

Another related question.... Using Pool Math, if I want to SLAM a bromine pool (with no CYA), do I calculate the required liquid chlorine to raise FC to 10... which raises bromine to over 20?

Example: (Using rough numbers)... Bromine @ 6 ppm = FC @ 3 ppm
To raise FC to 10 ppm (bromine to 20 ppm) in a 20k pool, I would add 2 gallons, 3 cups of liquid chlorine bleach (12.5%)

State regs say no swimmers are allowed in pool if bromine is over 10 ppm, so then we would have to wait until the bromine reading drops to that level before opening the pool again. Does this all sound correct?

Thanks.