Black stain caused by worms?

[JoannaB]

Uncovered our pool to vacuum yesterday, which I have to do several times during the winter due to all the worms and fir needles we get (even tho it's covered!) After cleaning up the usual big clump of worms in the bottom there was a large black spot about 8"x 5" irregular in shape, right where the worms and needles were lying. I tried brushing it with the long-handled brush but it didn't budge. The pool is not open and 60 degrees so I'm not going in for a closer look yet. Any advice on how to get rid of it before I open the pool or will I have to wait?

 

[mknauss]

Do you have a trichlor tablet? If you do, and you can get to the spot, put the tablet on the spot for 10-15 minutes, no longer. If that lightens or removes it, it is an organic stain that will disappear over time with proper chlorination levels.

 

[JoannaB]

I have dichlor sticks I don't use anymore. But if trichlor is more effective I can get some.

 

[mknauss]

The dichlor will work if they do not dissolve too fast.

 

[JoannaB]

Thanks. I'll try it. I just got my CYA under control at the end of the last season by draining half the pool and switching over to the TFP method, so I'm loathe to put any sticks or tabs in the pool. Here's a pic of the quite large stain. I'm afraid quite a few will be required. Hopefully my CYA will not be effected too much.

 

[mknauss]

Use PoolMath, Effects of Adding Chemicals, to see what effect one stick would have.

Though, hopefully, it will not fully dissolve in a few minutes. Do not let it sit in spot more than 10 minutes or so.

 

[bmoreswim]

I had some pretty noticable organic stains from worms and/or leaves this spring. They were gone within 24 hours with a slightly elevated FC level. So once you confirm the nature, you should be all but set.

 

[JamesW]

It should resolve within a few days once you get the chemistry right. I would wait to see if it clears up on its own.

 

[JoannaB]

Just an update: balancing and adding bleach is clearing up the stain. Thank you all!

 

[ShrinerManSC]

I have some black spots on the bottom of my 24,000 gallon fiberglass pool. Pool chemistry seems good and we have tried to brush them but they won’t come off and it’s in the deep end. Any ideas