Hi I have a 15x30 salt pool here in south Florida. I had a new diamond bite surface about a year ago. We have had a lot of rain here and the past few days I found about 20 circular light blackish stains on the bottom in various areas. I tried a metal brush, vitamin c tablets and a black algae treatment(pretty sure it’s not black algae as I had it a few years ago and it looks completely different, no head) Today I tried a spray gun with muriatic acid and it didn’t effect the spots at all. Think it made it worse, possibly. I’m at a loss for what to try next. Went to Leslie’s and they tested water and said it was prefect except for salt content. So I think I quite possibly had low chlorine levels for a few weeks due to chlorinated not working and tons of rain. Please help! Thanks
Black dusty looking spots, help!
- Thread starter Johncdbass
- Start date
Do not buy or use any more "black algae treatment" for any reason even if you think you have Black Algae again. Just use chlorine and brush the heck out of it. Chlorine is all you need. 
Now, it sounds like organic stains, probably from not enough chlorine. If you have any chlorine tablets, or can borrow one LOL, place it on one of the spots and see if it lightens or goes away. If it does then it's organic and you need to run your chlorine at a higher level for a few weeks (So if your min/target levels are 4-5, then you should run it at 7-9), and brush the areas frequently, and they should fade. If they go away, and you lower your FC level to "normal" and they return, then your "normal" level needs to be higher, and you may have a very high CYA level.
How do you test your pool?
Do you have a full set of results you can share?
Now, it sounds like organic stains, probably from not enough chlorine. If you have any chlorine tablets, or can borrow one LOL, place it on one of the spots and see if it lightens or goes away. If it does then it's organic and you need to run your chlorine at a higher level for a few weeks (So if your min/target levels are 4-5, then you should run it at 7-9), and brush the areas frequently, and they should fade. If they go away, and you lower your FC level to "normal" and they return, then your "normal" level needs to be higher, and you may have a very high CYA level.
How do you test your pool?
Do you have a full set of results you can share?
Do not buy or use any more "black algae treatment" for any reason even if you think you have Black Algae again. Just use chlorine and brush the heck out of it. Chlorine is all you need.
Now, it sounds like organic stains, probably from not enough chlorine. If you have any chlorine tablets, or can borrow one LOL, place it on one of the spots and see if it lightens or goes away. If it does then it's organic and you need to run your chlorine at a higher level for a few weeks (So if your min/target levels are 4-5, then you should run it at 7-9), and brush the areas frequently, and they should fade. If they go away, and you lower your FC level to "normal" and they return, then your "normal" level needs to be higher, and you may have a very high CYA level.
How do you test your pool?
Do you have a full set of results you can share?
ok so here are my numbers
fac 4
tac 4
salt 4500 normal for my clorinator
ch 330
cya 80
ta 80
ph 7.0
copper 0
iron 0
phosphates 100
temp 85
I bought some chlorine tablets to put on the spots. How long should they stay on there? Thanks so much!!
If it's organic, a few minutes will fade the spots.
Now, on to those test results.... they are from a pool store, and unfortunately pool stores are notoriously inaccurate. I suggest you order the TF-100 or the Taylor K2006. Take control of your pool by testing yourself and you will be alot better off.
So their test shows no copper. You mentioned above that when you directed muratic acid on the spots it seemed to make it worse, that sounds like what happens with copper stains. So I'm curious to see what your tablet-test reveals...
I rubbed the tablets on the spots and they did absolutely nothing. I have a 4 stage test kit and all my numbers are in good range. I had black algae two years ago and the black spots had fuzzy hearts that eventually rubbed off. This is a new surface this year and the spots don’t seem like the same like last t8me. There is no fuzz or head. Very disappointed as this is a new surface which we had installed about 7 months ago. My water looks crystal clear right now. Any other ideas? Ps thanks so much for your help!
i know this is a totally stupid idea but is it quartz in the diamond write. i have super blue but there are some black quarts specs in the plaster its self. i was wondering as they started to show up as i brushed from day 1. i know stupid but it's what i instantly thought of when i read this.
Here are some pics. This is turning out to be very interesting. I have tried, vit c, clorine tab, bk algecide, copper treatment, muriatic acid, scrubbing. Idk what else??
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Here are some pics. This is turning out to be very interesting. I have tried, vit c, clorine tab, bk algecide, copper treatment, muriatic acid, scrubbing. Idk what else?? There are about 20 spots
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Just came back from two weeks away and found a few more spots. This has to be black algae I would think. Any ideas? Moderators, members, God?