Algae Blooms

General Discussion
1

In France we seem to get two algae blooms each year and one is normally in the first week or thereabout of August. This morning I have been contacted about two pools that have just turned green so as a warning to pool owners to make sure their chlorine levels are kept up normally but especially now, a bit more chlorine won't hurt and could save quite a bit in trying to fight the algae once it has established itself.


Also to remind people that packaged for forms of chlorine (galetts, lent and choc) all contain stabiliser (CYA) this could mean if you are using those and your stabiliser level is already on the high side you could push it further. liquid chlorine like eau de javel doesn't contain CYA and is cheap from a Brico, doesn't take time to dissolve.

2 Likes
2

Thanks John... useful info. I had a problem a few weeks ago when we went away for 3 days, summer cover on, and the chlorine ran out - nice green pool on return! An overnight 'shock' treatment and filtering till clear did the trick, Will keep an eye on it now the weather might be hotting up again!

1 Like
3

Interested in algae right now, mostly because the tiny river that supplies household water, as of right, is almost entirely covered in bright green xyz. I suppose, algae.
I never have any kind of hay fever, but this year, is different, possibly because of algae.
Don’t know, anyway…I have searched for algae info for this area, but its too small to be newsworthy, and so wondered if there are any algae expert peeps, out there, to advise, please?

I read about men, dogs and other animals dropping dead, that ventured into algae that look similar on photos from USA. And far off Breton coast,

But not a squeak about it …anywhere in, 35, so far.

4

Hi Jeanette, the drop dead algae is blue/green algae and is actually a cyanobacteria.
It’s becoming a real pest.

1 Like
5

Hello John, its quite seriously toxic, yes? However, shades of green are infinite. This stuff just looks green to me…but maybe blue to somebody else. The whole surface of the river is quite still …and covered with it, except when it rains. Yikes!! I think it must be the drop dead kind, here… That’s terrible!
Found a photo…

13156597

6

…Dans les lacs, les cyanobactéries se repèrent facilement car elles forment une couche verte, parfois bleutée, à la surface de l’eau. Cette masse peut mesurer plusieurs milimètres d’épaisseur dans les cas les plus importants.

Dans les rivières, elles sont plus difficiles à repérer car elles sont présentes au fond de l’eau. “Elles sont très foncées et forment de petites taches noires.” Lorsque leur prolifération est intense, elles peuvent prendre la forme d’un amas spongieux qui flotte à la surface. “Il s’agit de biofilm, un assemblage de micro-organismes qui était collé à un galet dans le fond de l’eau, par exemple, et qui s’est décollé” , reprend le chercheur Jean-François Humbert.

Généralement, ce sont ces biofilms qui posent le plus de problème : le risque pour les animaux de les avaler ou pour les enfants d’être en contact est plus grand. Leur présence peut conduire à des interdictions de baignade ou de pêche. Le 22 août, la préfecture du Maine-et-Loire a pris un arrêté de suspension de la pêche professionnelle afin d’éviter que tout poisson contaminé soit consommé. En revanche, les pêcheurs à la ligne sont toujours autorisés, “s’ils pratiquent la remise à l’eau” , précise Mathieu Bodin, directeur de l’association des pêcheurs professionnels en eau douce du bassin Loire-Bretagne, à franceinfo…

7

Algae information.
Never let your dogs jump into it.
8

Thanks John for this advice; I wish had read it 10 days ago!
I used Bayrol Chlorklar pastilles; discovered that my pool stabiliser was already high, after pastilles higher still. Unfortunately its not possible to empty half the water then add more to reduce stabiliser at my home and am now in a spiral of slightly green pool, new guests (paying!) and have been forced to used H2O2; I have just started a thread called H2O2 how much? how often? Could you possibly have a look, I have read a lot of your advice it is extremely good ( I think so anyway)
Best wishes, David

9

David who forced you to use hydrogen peroxide?
It’s the sort of advice French pool shops give.
As you are no doubt aware the cost increase would buy a lot of Brico eau de Javel. It would have been better to counter the CYA with a higher level of chlorine.
Hydrogen peroxide is a stronger oxidiser but not a better bactericide and breaks down pretty quickly unless it’s stabilised with silver.