Is this algae?

[jandersen13]

Hi everyone,

This is my first spring with our pool as we moved in last summer in July. We had the pool opened by a pool company and everything was good. It was dirty on the bottom throughout this spring with some leaves, flower petals, dirt, and pollen. We purchased a Dolphin M400 and that helped a lot. We are still getting pollen that seems to settle to the bottom even after using the Dolphin. I'm just guessing there is still a lot floating around. I started to notice some discoloration on the vinyl liner but thought it would go away. It looks like a tan / light brown film. I can't brush it off and I even turned the brush over to use the rubber end to see if it would rub off with something more heavy duty than the brush. It did not though.

Last week the pool went really cloudy after being crystal clear all spring. I added some chemicals recommended by the pool store (phosphate remover and clarifier). I then shocked the pool with 3 bags of 12 oz shock (28,5000 gallons). It cleared up a day or so later. We have still been getting lots of what I believe is pollen on the bottom. But the tan / light brown film still will not go away. I'm afraid that it is algae but don't know how to diagnose it for sure. I thought that if it was algae it would brush off, but it definitely does not.

Also when the pool was cloudy the chlorine was extremely low. After the shock it was very high for a few days and then came down a bit. Now it is starting to get lower again. I'm nervous it will get cloudy again as the chlorine dips. We use Brite Stix chlorine tablets in the 2 skimmers we have (1 in each).

I've been reading this forum for a little while now and I know your opinions are to not do what I am doing with the chemicals. I'm hoping you can still be of some help to get this tan / light brown film / stain diagnosed. Any help would be great.

I have attached some pictures for you to see what it looks like.

 

[Divin Dave]

Hard to say from pics. It might be.

The best way to tell is to have your own recommended test kit and do a couple of water tests.
The Cobmined Chlorine test and the Overnight Chlorine Loss Test will tell you for sure.

Can you brush it off? If you can, then its definitely algae.
Have you felt of it with your hand in any way? Is it rough textured? or slimey?

 

[jandersen13]

Dave,

I'll look into getting a test kit. How would I tell from the combined chlorine test and overnight chlorine loss test? Is there a certain number I'm looking for here? Any further explanation would be great.

I can't brush it off. I brush really hard and it does not seem to move / clear off at all. I have not felt it though.

 

[jandersen13]

Dave,

Looked around a bit more and I believe you are referring to OCLT, is that correct? Pool School - Perform the Overnight FC Loss Test (OCLT)

- - - Updated - - -

One more question. If I perform the FAS-DPD FC test it says to not add chlorine. Should I take the Brite Stix pucks out of the skimmers when doing this test overnight? Should I keep the filter running all night?

 

[DanielP]

Yes he's referring to the OCLT and don't add chlorine in any fashion, including tablets in a floaty or feeder or skimmer. If you don't leave pump on you need it to start 30 minutes before testing. You can leave it running overnight if you want, it will help clean the water.

 

[jandersen13]

I ordered a TF100 Test Kit last night. It will take a few days to come in though. Anything I should do in the meantime? Anyone else out there that has any thoughts on what the discoloration may be?

 

[jandersen13]

Hello? Can anyone help out there? No one has any idea what that discoloration on the liner is? No one has experienced this before?

 

[Richard320]

Yes, remove any source of chlorine while doing the overnbight test.

If you didn't lose any FC, it's not algae.

Do you have hard water? That sort of looks like scale. It can be beige or greyish. It could also be organic stains from the compost pile you had in the pool, and a few weeks with normal chlorine levels should bleach it out. Or it could be metals if you ever used a mineral system, or copper-based algaecide. That one is easy to test. Get a cheap generic Vitamin C tablet and set it on a stain for about ten minutes. If it leaves a nice clear dot, it's metals.

 

[jandersen13]

Richard, thanks for the reply.

When you say to remove any source of chlorine while doing the test, you mean remove the brite stix from the skimmer but still have the pump running?

We don't have hard water and we are on city water here in Grand Rapids, MI. If it is an organic stain and just needs regular chlorine levels how do I keep them up as they seem to be going down very quickly within a matter of days.

We've never used a mineral system. They did put in algaecide when the pool was opened. I don't think it was copper based, it is called Regal Poly-Algaecide 30.

I will go out and get a vitamin C tablet tomorrow to test.

 

[Richard320]

Yes. Remove the sticks. You're looking to see if you lose any FC to organics - algae. By doing it overnight, you've eliminated the sun removing it. By removing the sticks, you've eliminated them from adding any more. Full instructions

If something is consuming your chlorine, you kill it. And then your FC loss will go down to something manageable like 2 or 3 ppm per day. Remember, bleach (or sticks) is a consumable item. You have to feed the pool daily.

Before you go buy a Vitamin C tablet, ask around. You only need one or two. Surely you must know some kind of health conscious person or a hypochondriac who can spare them.

 

[jandersen13]

Ok, I'll remove the sticks and test once my test kit comes in (hopefully soon).

Good idea about the vitamin c tablet!

I'll let you know the results.

 

[jandersen13]

I got some Vitamin C tablets today and placed 2 in the pool on the stain. It cleared it to the blue liner in about a minute or even less. So does this mean I have metal stains for sure? What should my next steps be?

 

[Richard320]

I got some Vitamin C tablets today and placed 2 in the pool on the stain. It cleared it to the blue liner in about a minute or even less. So does this mean I have metal stains for sure? What should my next steps be?

Here's the next step. I've never done it, so finding the link is as much help as I can give now.

 

[jandersen13]

Thanks Richard! I'll try that out.

 

[jandersen13]

I received my TF-100 test kit today. I tested the water and here are my numbers:

4 FC
0.5 CC
7.5 PH
275 PPM CH
120 TA
70 CYA

Can anyone weigh in on how these look? Would these numbers have any effect on that stain on the liner?

 

[Richard320]

I received my TF-100 test kit today. I tested the water and here are my numbers:

4 FC
0.5 CC
7.5 PH
275 PPM CH
120 TA
70 CYA

Can anyone weigh in on how these look? Would these numbers have any effect on that stain on the liner?

The Free Chlorine is too low for that CYA. If Vitamin C erased the stains instantly, it's metals. Nothing in your other chemistry would cause staining like that.

 

[jandersen13]

What should I get my FC up to for that CYA?

 

[crek31]

Read around Pool School for some of the answers you pose -- once you get your test kit and run a few tests, stuff will start to click pretty fast. The more Pool School you read between now and then, the better. One of the gems in Pool School is a chart showing how much FC is needed for what amount of CYA -- be sure you look at the table for no saltwater generator (assuming from your sig line you don't have one). Here is a link to the FC/CYA Chart:

Pool School - Chlorine / CYA Chart