Green Water - Algae?

[donovan.lambright]

Hey everyone! Before I tell my story, some numbers. I have the Taylor K-2006 test kit and here are the current numbers (that I think are relevant to my situation):
FC: 4 ppm
CC: 0 ppm
pH: 7.4
CYA: 45

My 15' Intex Ready Set pool has suddenly developed green water. For the past few weeks, I've been keeping the FC levels around 8 to 10 ppm using trichlor tabs. Based on the Best Guess Swimming Pool Chlorine chart, I finally decided that was higher than needed and scaled it back about a week ago to the 4 to 6 range.

About that same time, I noticed that the amount of dirt and junk in the bottom of the pool had dramatically increased. So, I vacuumed (twice). And the water has been green ever since. The junk picked up by the vacuum was mostly a fine sandy grit along with some grass clippings.

Since I've kept my FC up (testing at least once per day), I wrote the greenness off to me just dispersing some of the dirt into the water. I swapped out the filter and have been running it 24 hours/day. But it's been a couple of days now and the water is still quite green.

Tonight, I pulled out the filter that I installed yesterday to put in a clean one and noticed that it also is very green. Which got me thinking that I might have algae after all. The filter is one of the little ones that comes with most Intex pools. I use unicel filters, which get swapped out every 4 to 7 days.

My gut still says it can't be algae but the green filter has me a little spooked. The vinyl walls of the pool do not feel slick or slimy at all.

Any thoughts or suggestions? I'm thinking about using liquid bleach to shock the pool and see what happens.

One other thing: I know some of the above conflicts with the information in my signature. That data is out of date but I can't seem to change it; I just get an error message when I try to save the updated text.

Thanks!

Donovan

[Watermom]

What kind of trichlor tabs do you have? Any mention of copper in them?

[donovan.lambright]

Hey Watermom! I don't have the container anymore, having put the last tabs in my floater. I do know the container said 99% trichlor with no mention of copper. After the problems I had last summer with daughters skin reactions, I learned to be pretty careful about additives

Sorry not to be more concrete.

[Watermom]

How have you been keeping the chlorine high with only trichlor tabs?

[donovan.lambright]

About a month.

[PoolDoc]

+ Dose your pool in the evening with bleach to take levels 15 ppm or higher -- 1/2 - 3/4 gallon of bleach should do it.

+ Brush your pool thoroughly the following AM.

+ Continue to dose with bleach in the PM to 15+ ppm, for 3 days after there's no green anywhere. (A gallon of 8.25% bleach will add ~20 ppm to your pool.)

[Watermom]

I think you misread my question. I wasn't asking you how long you have been using trichlor to keep chlorine level elevated but how you were doing it. You cannot shock a pool with trichlor tabs. My recommendation was going to be the same as Ben's above. Use bleach to shock the pool.

[donovan.lambright]

You're right, I misread the question. I shocked the pool with liquid bleach last night. This morning, the FC was 16 ppm. The water is still greenish and there is a yellowish layer of something on the bottom.

[PoolDoc]

Keep it high, and BRUSH it!

[donovan.lambright]

Will do.

If this is algae, I'm puzzled as to what happened. I opened the pool using liquid bleach and only switched to trichlor after the FC levels were established. I checked it at least once per day and it never got below 4 ppm. Mostly, it was in the 6 to 10 range. What am I missing?

[PoolDoc]

There is another possibility. If the tablets had copper in them, copper can stain filters bluish green, and sometimes color the water. If you post a picture -- just supply the link -- to Flickr, Facebook, Webshots, whatever, I can probably tell the difference between algae and something else. If you use Facebook or some similar services remember to make the picture visible to the "world".

[donovan.lambright]

Here's the link. Took this a couple of hours ago.

https://www.dropbox.com.KILLED/s/pan1lcxb3kzxwku/2013-07-26%2018.37.00.jpg
https://lh5.googleusercontent.com/-1sT0z0Ugr-s/UfMp0cVECDI/AAAAAAAAF7k/uv5hGAND2vc/s640/0WnI.jpg

[PoolDoc]

DEFINITELY, algae!

Add 2 gallons of 8.25% bleach, tonight if possible.

Get cheap OTO kit and test chlorine following night. If OTO light yellow, add 2 more gallons; medium yellow, 1 gallon, DARK yellow to ORANGE, 1/2 gallon.

Continue dosing nightly until pool has no green!

[donovan.lambright]

Add 2 gallons of 8.25% bleach, tonight if possible.

Done.

Still at a loss to understand what happened. I have the Taylor K-2006 kit and have been testing daily (sometimes twice a day). I'm pretty certain that I've been doing the FC, CC, and CYA tests properly but I can't think of any other explanation for how algae could have started when I've maintained (or so I thought) pretty high chlorine levels all summer.

[PoolDoc]

It looks like mustard algae. On some pools, it seems to take root almost instantly, if you let chlorine levels drop. Once present, it doesn't die unless levels are VERY high.

It's difficult to eliminate, but fairly easy to control on vinyl pools -- moderately high chlorine plus careful brushing will eliminate 99% of it quickly. BUT . . . it's not gone, and will return at the first opportunity.

It only lives where nothing disturbs the surface it's on -- thus, it often begins on the side walls in the deep end.

[donovan.lambright]

Makes sense.

As I think about it more, there was one day I let it drop to 3 ppm FC. With the CYA where it is (45), I suspect that's when it started. Grrr. I thought was going to have a trouble free summer.

But the good news is that the water was pretty clear this morning with a heavy yellowish layer on the bottom. I vacuumed it and swapped filters. It's green and cloudy again now, but that's just because my vacuuming stirred it up again. I'll let it settle down with the filter running and will vacuum again tomorrow. I'll hit it with another gallon of bleach tonight.

In one of your last posts, you recommended I get a cheap OTO kit. With the Taylor kit I already have, I wondered why. To keep me from using up all the expensive regent measuring the shock-level FC? Not a big deal; just trying to glean as much info as I can from this experience.

Anyway, thanks for everything.

[PoolDoc]

Yeah, an OTO kit allows you get a quick and dirty but reliable measure of your chlorine level. On my to-do list is to publish an extended color match on OTO, up to 50 ppm.

I'm going to be tied up, and mostly away from the forum for the next few days. But numerous people have reported that borate levels > 60 ppm have reduced their pools 'twitchiness', with respect to algae. If you want to look at that, I'll help you next week. On a pool your size, the cost would be negligible.

[donovan.lambright]

Sounds good. Thanks again!