Three heretical thoughts about fighting algae

[JasonLion]

I have been thinking about various ways to kill algae (regular green algae). Along the way I can up with three ideas that I think can help make the process simpler and more reliable. But they run against the common wisdom, so I thought I would ask for some comments and feedback to make sure I haven't completely lost my mind.

1) Wait till you are ready, don't just dump some bleach in and hope for the best. The typical advice is to get some chlorine in right now this moment and then add more as soon as you can. I think waiting till a weekend, or some other appropriate time, when you have enough chlorine on hand and can spend enough concentrated time to really deal with it is better. Too many people get into an endless cycle of adding chlorine once a day only to have the algae recover completely by the next day.

2) Make sure there is at least a little CYA in the water. The typical advice is to get some chlorine in there right now and deal with the CYA level when the algae is killed. Admittedly, it is difficult to measure CYA when the water is murky with algae and we don't want to add more CYA when the level is already too high. But often enough when people open for the spring the CYA level can be zero. If CYA is zero in an outdoor pool you lose chlorine to sunlight quite quickly. If sunlight drives FC to zero for several hours the algae starts getting ahead of us again and the effort and chemicals used to that point can be wasted. I think that adding 10 to 15 ppm of CYA, when there is any plausible chance that the CYA level is zero, could help.

3) Instead of testing FC and adding more chlorine to bring it back to shock level at least twice a day, how about doing that every half hour? I think Michael Silvester was on to something good when he suggested adding chlorine continuously until the water changed color. That doesn't sound quite right to me. Not everyone is going to judge color changes the same way. I worry about people using too much chlorine and possibly causing damage following his approach. What about going half way between the usual approach here (twice a day) and his: test and add chlorine every half hour? After a couple of hours of that the algae should be dead and the problem is solved.

I would appreciate any comments/feedback you might have.

 

[Hotrod30]

On your number one, when I was working, I would always wait until I had a 4 day weekend off to open the pool. Sometimes that meant string algae and a real green pool to start.

Number two I always started CYA raising on the second day in the afternoon; after the first vacuuming and draining down the pool level to acouple of inches above normal level.

Number three...... well I open my pool in what I thought was a strange way until I joined here. Even my wife thought it was strange using the socks for the CYA power tied off near the pool inlets.

To open the pool I go to Wal-Mart a couple of days before I open and buy 15 bags of shock, one gal of algicid, two tubs of CYA, two tubs of PH up, one pair of knee high socks and one 12 pack of beer. I don't even start filtering until the second day; just recirc.

But it works for me. It even killed black algae (or what ever it was, small black spots in one corner) I had one year. The same routine; but it works!

I still believe you have to 'learn' your pool.

 

[duraleigh]

Hi, Jason,

Good thinking and I see nothing heretical about them. My initial reaction is:

1) Couldn't agree more. The process goes so much quicker if the chlorine application is continuous. I do think it is important to convey to most people a small sense of urgency to minimize the amount of chlorine it will take to clear up the issue. That said, what has always seemed to me to be the ONE BIG ITEM that newbies fail to grasp is that the application must be continuous and that it is a process not a one-time cure. I like the idea of an organized approach with plenty of chlorine on hand and the time it takes to use it correctly.

2) While I agree in theory, the CYA may be a little harder to get folks to do. In particular, I think about the real newbies that have virtually no understanding of what chlorine does or why you put it in....much less the other parameters. Those folks might well be overwhelmed with how to calculate chlorine dosage, how to calculate pool size, etc. The additional info of CYA may add to their confusion. I might consider a greater benefit to emphasizewhen the chlorine is applied. I'm not sure we do that. I have always felt your inital dose of chlorine should go in about an hour before sunset....The UV rays are reduced to almost nothing. I like the idea of testing early next AM and dosing back again to shock level. If you get chlorine in their pre-dawn or so, you'll have several hours of effectiveness before the midday sun kills it. Then, repeat that twice-a-day application.

3) That is gonna' be tough to get the average pool owner to do. Spring weekends are filled with ball games, yard work, etc. and it will be difficult to convince folks they need to make that commitment. I certainly agree it would be a great approach but I'm not sure folks wouldn't decide that's too much work.

 

[chem geek]

1) For spring opening, I would agree that waiting until you have time to do more continual dosing is important. I'm not so sure about the beginnings of an algae bloom during the swim season at the dull/cloudy stage or early green stage. In that case, if you hit it hard early, you can stay ahead of it with far less chlorine as it won't get consumed as quickly nor in as large a total quantity. In the early stages, even once a day with a large dose of chlorine will help keep it at bay (unless the CYA level is through the roof or phosphates are >> 3000 ppb).

2) If one suspects there isn't any CYA, then adding some is helpful. Though one could use CYA in a sock, I think for fighting algae since one wants to add chlorine anyway then this is a perfect time to use Dichlor which dissolves very quickly and it's not that much more expensive than using chlorinating liquid or bleach plus CYA separately (see this post for some cost analysis). Again, it's likely that there is CYA in the water unless its spring opening; during the year, anyone using stabilized chlorine (e.g. Trichlor) certainly has CYA in their water.

3) If there's CYA in the water, then it's hard to go overboard with the chlorine level unless one goes well above the FC 60% of CYA that is the yellow/mustard algae shock recommendation. Of course, one must know roughly how much CYA is in the water since if there isn't any or not very much, then one could over-chlorinate although it should be brief since the chlorine will get used up quickly oxidizing the algae. Michael's visual procedure is probably reasonable for this reason so long as you space out your additions by about a half hour and do perhaps 10 ppm FC at a time (more if the CYA level is high).

Richard

 

[IkeRay]

I have been thinking about various ways to kill algae (regular green algae). Along the way I can up with three ideas that I think can help make the process simpler and more reliable. But they run against the common wisdom, so I thought I would ask for some comments and feedback to make sure I haven't completely lost my mind.

1) Wait till you are ready, don't just dump some bleach in and hope for the best. The typical advice is to get some chlorine in right now this moment and then add more as soon as you can. I think waiting till a weekend, or some other appropriate time, when you have enough chlorine on hand and can spend enough concentrated time to really deal with it is better. Too many people get into an endless cycle of adding chlorine once a day only to have the algae recover completely by the next day.

2) Make sure there is at least a little CYA in the water. The typical advice is to get some chlorine in there right now and deal with the CYA level when the algae is killed. Admittedly, it is difficult to measure CYA when the water is murky with algae and we don't want to add more CYA when the level is already too high. But often enough when people open for the spring the CYA level can be zero. If CYA is zero in an outdoor pool you lose chlorine to sunlight quite quickly. If sunlight drives FC to zero for several hours the algae starts getting ahead of us again and the effort and chemicals used to that point can be wasted. I think that adding 10 to 15 ppm of CYA, when there is any plausible chance that the CYA level is zero, could help.

3) Instead of testing FC and adding more chlorine to bring it back to shock level at least twice a day, how about doing that every half hour? I think Michael Silvester was on to something good when he suggested adding chlorine continuously until the water changed color. That doesn't sound quite right to me. Not everyone is going to judge color changes the same way. I worry about people using too much chlorine and possibly causing damage following his approach. What about going half way between the usual approach here (twice a day) and his: test and add chlorine every half hour? After a couple of hours of that the algae should be dead and the problem is solved.

I would appreciate any comments/feedback you might have.

I was thinking over this post while beginning to reopen my pool today, and like chemgeek/richard suggested, dichlor would take care of 1 and 2. what i mean is, if you have an inline chlorinator installed, throw 3-4 tablets in there and crank it up to 1/2-3/4 (or higher, i dont know the level to do) or throw in a floating chlorine tablet things. it would be more convenient for the people who can't devote lots of time to opening the pool, and sort of takes care of "3" as well. i would still recommend checking on it fairly often, and maybe even still use liquid sodium hydrochloride to shock the pool, but the tablets will help to keep the levels up, even if you don't have time to re-up the chlorine levels.

also, in the CYA area, if you had high levels last season before closing, i wouldnt worry about adding in CYA as you dont want to completely overwhelm the pool with CYA.

or i might just be a complete idiot...just what i thought of. i guess people arent lucky like me where im home all week long and have plenty of time to devote to the pool when need be.

 

[JohnT]

2) Make sure there is at least a little CYA in the water. The typical advice is to get some chlorine in there right now and deal with the CYA level when the algae is killed. Admittedly, it is difficult to measure CYA when the water is murky with algae and we don't want to add more CYA when the level is already too high. But often enough when people open for the spring the CYA level can be zero. If CYA is zero in an outdoor pool you lose chlorine to sunlight quite quickly. If sunlight drives FC to zero for several hours the algae starts getting ahead of us again and the effort and chemicals used to that point can be wasted. I think that adding 10 to 15 ppm of CYA, when there is any plausible chance that the CYA level is zero, could help.

I can't disagree with any of it, but it may not be possible to know what your CYA level is when the pool is full of algae. Mine read 35ppm last spring, but when I cleared the water, I could fill the tube and still see the spot. If it happens to me again, I'll have a pretty good way of guesstimating by the reduction in my alkalinity, but no way to know for sure.

 

[JasonLion]

A limited amount of dichlor would be a good approach to adding CYA since the CYA would become available right away and you want the chlorine. Still, as duraleigh suggested, there is a risk of confusing things further by adding any additional complications, such as using managed amounts of dichlor and then switching to bleach.

Trichlor in tablets/pucks would not work well. Trichlor tablets are designed to dissolve slowly and what we are trying to achieve is a very rapid introduction of chlorine. Trichlor is in the same category with a SWG or Liquidator, they are all designed to introduce chlorine slowly. That can be a handy way to help maintain shock level once you have already gotten there. But to get the initial shock you want the chlorine to all become available at once.

The real beauty of Michael Silvester's system is that it is very simple for novices. I would like to try for some of his systems advantages, while promoting some of the values espoused here, specifically water testing and getting chemicals to predetermined goal levels, all while resolving some of the common problems (no test kit, only adding chlorine once a day, etc). It becomes a balancing act. How much can be stuffed in and still not intimidate novices too much, all while keeping it maximally effective.

 

[duraleigh]

The real beauty of Michael Silvester's system is that it is very simple for novices. I would like to try for some of his systems advantages, while promoting some of the values espoused here, specifically water testing and getting chemicals to predetermined goal levels, all while resolving some of the common problems (no test kit, only adding chlorine once a day, etc). It becomes a balancing act. How much can be stuffed in and still not intimidate novices too much, all while keeping it maximally effective.

Good paragraph, Jason. Is there a link to reading more about Michael's ideas?

 

[JasonLion]

You can read his approach to algae in this thread along with several responses from people here (including you duraleigh). Or you can go to Michael's site, which is a hard sell for his newsletter. If you sign up for the newsletter there are a couple of other wonderfully written articles you can get and some very funny stories.

Skipping over the fact that Michael is a great writer, the essential method is to adjust PH, add chlorine till the water changes color, add floc, let it sit overnight, and vacuum to waste.