Persistent Algae

[mbaker]

Hi All,

I've been trying to resolve an issue with green algae in my pool. For the past couple of weeks I've been following the SLAM guidelines documented here to the best that my schedule allows and don't seem to be making any progress. The pool isn't getting worse but it's not getting better.

Attached is an image of what the pool looks like. Ignore the rough shape of the structure and liner. This thing is on its last legs!

Levels before beginning the SLAM were:
FC: 0.6
CC: 0.2
pH: 7.7
TA: 90
CH: 250
CYA: <30 (best guess 20)

Note: When needed, the pool is refilled with well water. The water runs through a softener but there's no way it keeps up during the full pool fill. Unsofened, the water is:
Iron: 0gpg
Hardness: 25gpg

I first lowered the pH to 7.6 with Muriatic Acid. Confirmed with test.

Then I started to SLAM.
General schedule:
- Test first thing in the morning
- Test at ~8pm at night
- Manually vacuum from ~8pm-9pm most nights
- Empty strainer basket 1-2 times per day as needed
- Backwash filter and empty pump basket every 2-3 days as needed

Action log (rough at the start but gets more detailed as we go!)
Day 1-2: I added a total of 10.4 L of 10.3% bleach to keep FC at or above 10. After the first day the FC never tested below 12.
Day 3-6: I went through 7.4L of 10.3% bleach to keep FC above 12 and CC dropped to 0.1.

Day 6-9: I ran out of bleach and didn't have access to a car for 3 days so I added 800g of Trichlor pucks spread over those days to try and keep FC up. I figured (mistakenly?) that I could use some more CYA anyway so it wasn't the end of the world. During this time the FC crept up to 16.5 but the CYA didn't noticeably.

Day 9-10: Once I had a car again I picked up some dry CYA and a bunch more bleach. I added 400g of dry CYA and continued maintaining FC with bleach. Once the CYA disolved this is where my values were at:
FC: 16.5
CYA: 30

With the increase in CYA I decided to target an FC at no lower than 14 for each test. Just in case something came up and I missed a morning or night test.

Day 11: FC at 14, Add 3.6L of bleach
Day 12: FC at 17.5 in the morning and 17 at night (a really cloudy day with rain coming at night)
Day 13: FC at 15 in the morning, add 3.6L of bleach. Got home too late to test but added another 3.6L of bleach at night.
Day 14: FC at 14 in the morning, add 3.6L of bleach.

At this point I'm starting to wonder if maybe I have mustard algae?
Backwashes of the filter are pretty green but clear up much faster than I've seen when the filter is really full.
When vacuuming during the early days of the SLAM the water running through the pump was quite green and I did vacuum up quite a bit of white flakes (calcium?). Probably a pump basket worth.

I'm betting the flakes came from my previous attempt to open the pool where, at the advice of then local pool store, I burned through ~3Kg of Cal-Hypo about a week trying to get rid of the algae before finding TFP and getting a proper test kit.

I think I've been pretty thorough reading through existing forum posts, understanding the tests (including Taylor K-2006 manual), and read through the Pool School posts here. We really haven't been able to enjoy the pool at all this year and I'm starting to run out of ideas. Maybe someone more experienced than me sees a glaring issue or has advice on the best course of action?

Otherwise I think my options are one of the following:
- Raise FC to try a mustard algae shock
- Drain the pool down to the return and deep clean the sand filter.
- Drain the pool completely, pressure wash liner, re-fill. The pool is so old I'd be worried about the liner shrinking/drying out and breaking it. If it did work, I'd probably call it for the season and try again next summer.
- Ditch the pool and think about getting in line to get a new one in a few years (current wait time is ~2-3 years).
- The pool is getting long in the tooth (~15 years) with some uneven pits in the floor of the pool and liner slipping on the sides in some places.

 

[Texas Splash]

Welcome to TFP! That IS a green pool - too green perhaps. Makes me wonder about metals content. Not sure how you are able to confirm no iron, but wells are certainly prone to having it. While we see many AGPs with brown ice-tea water from iron, metals can results in odd color changes. Have any copper products been used in the past like algaecides, or sanitation products called something "Blue"?

If we get past the metals aspect of the water, algae cannot survive in properly chlorinated water. If your testing has been accurate as noted above, a CYA of 30 only requires an FC of 12 to be at SLAM level. From there, the SLAM Process does the rest. If you haven't performed a deep clean of the sand in the last year or two, that may be next but it doesn't justify the extremely dark green water.

 

[jeffchap]

How often throughout the day are you testing and adding chlorine? The SLAM protocol says a minimum of 3 times per day, but I prefer at least 4. Hourly is best if you're available to do it. The more times per day you dose, the faster the SLAM works.

 

[mbaker]

Certainly too green!

Not sure how you are able to confirm no iron, but wells are certainly prone to having it.

I suppose I haven't confirmed no-iron in the well water for some time but part of the water potability and softener configuration includes testing for iron. The house is ~25 years old and I have the previous owners original water test results from the lab as well as a few tests that I did myself with reagents a couple of years ago. All results came up 0.

Have any copper products been used in the past like algaecides, or sanitation products called something "Blue"?

Now that you mention it I did put in an algaecide as part of an opening package that the pool store pushed on me at the start of the season. I don't know whether it was copper based but I'll go back to the store and confirm the product on the shelf. That's a good theory!

If you haven't performed a deep clean of the sand in the last year or two, that may be next but it doesn't justify the extremely dark green water.

Hmm, ok. Good to get confirmation that a filter PROBABLY wouldn't be the cause of an issue like this but that's what I was leaning toward trying next.

At least I have a couple of leads. Will report back!

 

[mbaker]

How often throughout the day are you testing and adding chlorine? The SLAM protocol says a minimum of 3 times per day, but I prefer at least 4. Hourly is best if you're available to do it. The more times per day you dose, the faster the SLAM works.

Almost always 2 times per day and always before I add any chemicals. Since the first day the FC level has never read below the recommended SLAM level for my current CYA level. Maybe I've misunderstood that FC only goes down over time and never up without adding bleach. That should mean that the FC level has never gone below the amount I test at right before more bleach is added.

I would love to test more often but it's just not feasible for me. That's what I've been keeping the FC higher than recommended. To give me some buffer from unexpected FC drops.

 

[Mdragger88]

If u did have mustard algae- you would follow the SLAM Process to completion anyway (meeting All 3 end of slam criteria) BEFORE raising to Mustard Algae slam level for 24hrs. So, if u have your suspicions you can do this at the end if u wish.
I agree, it is quite green… that could just be the algae since u aren’t able to test & replenish slam level more than twice per day. It can make the process take a while.
Many pucks & powdered shock products contain copper - if u have been using those before now it’s possible that’s part of the culprit w/ the vibrant color or it could be the iron from the well water. At any rate clearing algae is the 1st priority. You can try adding some polyfill (pillow stuffing) to the skimmer while u r slamming & see what u catch, it may confirm iron is partially to blame. Keep slamming & let us know how it goes.

 

[mbaker]

I very much appreciate the feedback.

If u did have mustard algae- you would follow the SLAM Process to completion anyway (meeting All 3 end of slam criteria) BEFORE raising to Mustard Algae slam level for 24hrs. So, if u have your suspicions you can do this at the end if u wish.

Ah, ok. I thought some Mustard algae cases remained green vs the quick returning variety. I'm really only suspecting mustard algae because for 2 weeks now I haven't seen any progress while slamming. This thread has given me some other avenues to explore though.

since u aren’t able to test & replenish slam level more than twice per day. It can make the process take a while.

I'm not sure I understand this part. If my twice per day tests before adding bleach always come in above SLAM levels how is that different than testing more often?

Many pucks & powdered shock products contain copper - if u have been using those before now it’s possible that’s part of the culprit w/ the vibrant color or it could be the iron from the well water.

Interesting. I just checked the pucks I have and they don't list copper but I'm learning most pool products are pretty sparse on the details.

You can try adding some polyfill (pillow stuffing) to the skimmer while u r slamming & see what u catch, it may confirm iron is partially to blame. Keep slamming & let us know how it goes.

First I've heard of polyfill. Looking at iron rich pool water that doesn't look like my pool but it's worth a shot. Who knows, maybe after hours of drawing from my well the water composition changes and does in fact have iron.

2 weeks into a SLAM and no visible progress I don't have my hopes up that staying the course is going to work!

 

[Mdragger88]

About mustard algae - here’s some info

Mustard Algae

Today We are going to show you how you can get rid of mustard algae in your pool. By following the steps in this guide and with no expensive chemicals.

www.troublefreepool.com

Are u certain of your cya level? If it reads anywhere between 30 & 40 it counts as 40 & slam level is 16ppm. There’s no inbetweens w/ the cya test, always round up. If that is underestimated it’s possible you actually weren’t at slam level most of the time.

If the trichlor doesnt say it’s
99% trichloro-s-triazinetrione or it says xtra blue or 4 in 1 or 3 in 1 it may contain copper. Although if all u have used in this fill of the pool is the amounts u mentioned that shouldn’t have that much of an effect.

Here’s some info about the polyfill-

If you’ve got iron in your fill water, use Polyfill to remove it

EDIT: Found out this method only works if your iron is oxidized already, meaning it’s got a dull or bright green tint to the water, or a nasty brown tint. If you know you have iron in your fill water, but it isn’t oxidized yet, bring your pool to shock level and it’ll turn the telltale green...

www.google.com

 

[mbaker]

Are u certain of your cya level? If it reads anywhere between 30 & 40 it counts as 40 & slam level is 16ppm. There’s no inbetweens w/ the cya test, always round up. If that is underestimated it’s possible you actually weren’t at slam level most of the time.

Oh I thought it was just round down...hmm ok. I was definitely well below 30 before I added CYA as the dot wasn't occluded at the top of the tube. After the 600g of dry CYA and the tri-clor pucks it was then maybe 3/4 of the way to 30 so I was rounding down. Good to know to always round up. I'll adjust target FC to 18 and see how things go. I know this is higher than required but giving myself some wiggle room to accommodate my availability.

My pucks say "ultra pucks"
100% trichloro-s-triazinetrione
90% Available chlorine content

This wasn't a fresh fill at all so who knows what else is in there. We'll see how this new target fares, I'll figure out what type of algicide was used earlier in the summer and get a hold of some poly-fil.

 

[Mdragger88]

Hopefully maintaining a fc of 16 will show some progress with algae. It seems u were already starting to hold fc pretty well, so that’s a good sign in the fight.
The nice thing about the poly fill method is that u need to have elevated fc chlorine which u already do when slamming so 2 birds at once kinda thing. It’s also a cheap, easy thing to try, it just takes time to filter out the iron. Some people wash out the polyfill when full & some just discard it. It’s not super expensive so I would probably discard it since u are dealing with algae too.
Aside from the color, How’s the clarity?

 

[mbaker]

The pool is looking a tiny bit less vibrant green today. Hopefully it keeps moving in that direction!

I ordered some Poly-Fil last night and should get it on Monday. We'll see what we can filter out. I'm really looking forward to deep cleaning the sand filter at the end of the season too now that I know about that.

Picked up 8 more jugs of bleach today. I really wish there was a place nearby that did liquid chlorine refills. Maybe if my work moves back toward the city I can start taking advantage of that. The number of jugs in my bin is out of hand!

I also verified the a algaecide I used earlier in the season. It was a 1L bottle of 40% Poly Alaecide. So I don't think it would have drastically affected my pool's chemistry. Obviously now that I'm following the TFP methods it's not something I'll put in again.

Clarity isn't good. It's hard to say but I think it has improved since I started. I can see ~12" down vs maybe 6" at the start. I certainly can't see the bottom of the pool while vacuuming at the moment.

Fingers crossed this is the start of seeing progress.

 

[Mdragger88]

Using a pool pole in the same place every day & taking a pic can help u see any improvement in clarity.

Be sure to do all these things to help move the slam along

*Check & scrub every nook & cranny where it may hide (light niches, drain covers, remove & scrub steps - they are algae hotels! , skimmer throats/weirs, weir door foam, etc.)
Anywhere water can go, algae will grow.

*Brush & or vac daily (this breaks up biofilms that algae uses to protect itself from chlorine) this also removes organics that are consuming your fc

*Backwash/clean filter when pressure rises 25%over clean pressure.

 

[mbaker]

I'm not gone, just too busy to post.
Pool has been making good progress! Here's some photos from Friday and today.
Today is the first day that I can finally see down to the bottom and find all the nooks and crannies that I've missed while brushing blind.
We're not totally clear and I'll still have to validate over night FC loss but everything is headed in the right direction. Fingers crossed that the pool is good to go this weekend.

 

[Mdragger88]

Great
Keep Slam level until u pass ALL 3 end of slam criteria. No need to do the Overnight Chlorine Loss Test until u are looking crystal clear unless u just wanna get an idea of what kind of loss you’re having .
It is safe to swim with fc levels anywhere between minimum & slam level for your cya so long as u can see the bottom of the pool for swimmer safety.