Algae on surfaces - what are visual effects of shocking?

[lalittle]

I recently shocked my pool, but a couple days later I noticed a few areas on the sides of my pool and spa that were a bit yellow. I'm honestly not sure if it was there before the shock or not, but I'm guessing that it probably was, and that I just didn't notice it yet since it was fairly innocuous. It easily brushed off, so it seems clear that it was algae, but I'm unclear what the visual results of successful shocking are. In other words, after shocking, can the yellowish color from algae still remain until you physically brush it off, or should the shock have made the yellow color go away if it was successful even without brushing? I'm not clear if the yellow after the shock indicates that the shock was not strong enough, or simply that it needed to be brushed afterwards in order to fully disappear.

It's been a few days and the yellow hasn't returned, but I need to know if I should once again shock the pool. Note that the water has remained totally clear throughout the process, and I have only minimal Chlorine loss overnight (about .4 ppm drop), and 0 CC in my readings (using the Taylor K-2006 kit.)

Thanks,

Larry

 

[PSW]

If you shocked properly, and maintained correct FC after, you should not get another algae bloom. If you are dealing with mustard algae, it is particularly difficult to get rid of..but once you eliminate it, FC will help prevent it.

Can you give us full test results? Also, a little more info about your pool (size? SWG? etc) would be helpful.

 

[lalittle]

It's around 22K gallons (including an attached spa.) No SWG -- I use a combination of liquid and tablets.

Just to clarify, is what I'm describing -- i.e. a couple areas with a little bit of yellow coloration on the wall -- still considered an algae "bloom"? I always thought that a "bloom" was when you had a sudden, rapid overabundance of algae in the pool rather than just a few spots on the walls. Is this not the case? I just want to be clear that other than a few yellow patches, the water looks totally clear.

That aside, I'm still not 100% sure what the visual effects of successfully shocking should be in the situation I'm describing. It sounds like you're saying that the yellow patches could still remain after the shock (until I brushed them) even though the shock had worked and the algae was now dead. Is this correct, or would the yellow be completely gone if the algae was taken care of? I just want to confirm whether or not the presence of yellow on the walls after the shock (prior to brushing) tells me anything. Once again, the water itself looks totally clear.

Regarding the chemicals:

FC (now) is around 4.5
CC = 0
pH = 7.4 to 7.6
CYA = 60ish
TA = 60 to 70

I realize that with a CYA of 60, I should shoot for a slightly higher minimum, but I've had good luck with slightly lower Cl levels over the past year. There were some heavy rains lately, however, and I accidentally let the FC drop way down, which I believe led to the algae growth.

Thanks again,

Larry

 

[lalittle]

A couple other questions:

Does the fact that the algae looked yellow mean that it was in fact mustard algae, or could other algae look yellow as well? I'm rather new to this, so I don't have much of a point of reference for what different algae looks like.

Also, is there a point -- i.e. some number of days -- where if the algae has not returned, I'll be able to assume that I've successfully taken care of it? I ask this because the algae showed up even though the overnight Cl loss test showed only minor drop. I'm therefore wondering if a visual inspection after some number of days would tell me if I successfully treated it.

Thanks,

Larry

 

[Butterfly]

I realize that with a CYA of 60, I should shoot for a slightly higher minimum, but I've had good luck with slightly lower Cl levels over the past year.

Running too low FC/CYA ratio is a recipe for mustard algae.

 

[macgulley]

Brushing is an important part of shocking. I'd guess you had a little green algae on the sides of your pool that you didn't notice. Green algae turns yellow/off white when killed and brushing it off to be filtered out is the correct action. Keep an eye on it but I think what you're seeing in normal.

 

[lalittle]

Brushing is an important part of shocking. I'd guess you had a little green algae on the sides of your pool that you didn't notice. Green algae turns yellow/off white when killed and brushing it off to be filtered out is the correct action. Keep an eye on it but I think what you're seeing in normal.

Thanks for the responses everybody.

Are there any other characteristics of the algae that could indicate what type of algae this most like is/was? I read that mustard algae tends to grow on the more shady sides of the pool, which is exactly where my patches were. Does green algae have the same tendency, or is this an indication that it was in fact mustard algae? I'm just wondering if I should do a regular shock, or a stronger mustard algae level shock.

On a similar note, does the fact that I didn't notice it until after I shocked indicate that it was more likely green algae? I was wondering if it's more difficult to notice green algae when it's green (since the color is closer to the turquoise pool color), and that after the shock turned it yellow, it became much more obvious.

Thanks again,

Larry

 

[macgulley]

I'd assume it's dead green algae unless it keeps coming back. pool-school/mustard_algae

 

[lalittle]

I'd assume it's dead green algae unless it keeps coming back. pool-school/mustard_algae

The artical states that mustard algae goes away during the shock, "only to reappear as soon as you come back down to normal chlorine levels." Does this mean that as long as it doesn't immediately reappear when I'm back down to normal Cl levels, I don't have a mustard algae problem? In other words, if I hold at normal Cl levels for a day or two without any reappearence of algae, can I assume that it's all take care of?

Thanks,

Larry

 

[macgulley]

I don't know how many days without algae would indicate green rather than mustard but if it keeps coming back I'd try the mustard level shock. Otherwise I wouldn't spend the money and effort that requires.