How To Safely Use An Algaecide In Your Pond

Pond algae will drive a person to do some crazy things.  I know, because I’ve probably done most of them.  Well OK, I haven’t done a half-naked “algae dance” around the pond in hopes of getting rid of it.  But I’ve thought about it.

One thing I have done, and I’m happy to say this was many years ago, is that I have misused an algaecide and paid the price for it.  Listen, I don’t blame anyone for wanting a quick fix to an algae problem.  If I could snap my fingers and have a perfectly clean pond every time I walked by a dirty one, I’d be pretty happy and probably quite rich. 

Sometimes though, quick fixes, come with a price.

Now for some of you who have read my material over the years, this may be old hat and routine stuff, but the fact is, every single spring and summer I get quite a few emails that tell the same sad tale.  It always goes something like, “Mark, I used this algaecide or whatever it was, and my green water or algae is gone, but all my fish died, what happened?”

That kind of email just gets to me.  It makes me sad because it was something that probably didn’t have to happen and so I can never preach this too much.  Please listen closely.

If you’re determined to use an algaecide in your pond, and particularly in a smaller pond, please be sure to not treat a heavily infested pond all at once.  Whether it’s green water or string algae or any other type of species, it doesn’t really matter, but you cannot kill too much algae too quickly or your fish will pay a price for it. 

The reason is that, as the algae dies off, it will pull a great deal of oxygen out of the water.  You can guess what happens to fish in an environment like this.  Many or all will die and will do so quite quickly. 

One safeguard you can put in place is to turn your aeration on (if you have it) full bore while you treat with a chemical.  The other is to be sure to treat only sections of the pond at a time.  In other words only treat a bit of the mass of algae every few days and knock it out gradually by topically applying or spraying the algaecide directly on or above the algae.  Do not simply dump a liquid algaecide into a pond and treat the whole thing at once if the algae is fairly heavy.

The same advice would go for green water (and quite frankly I’m not sure how you could safely treat green water with an algaecide but some folks probably do) and all other types of algae masses.

Also keep in mind that no pond is immune from this problem of oxygen deprivation.  To be sure, smaller ponds, being more “delicate” and susceptible to misdirected dosages, can be at more risk, but even larger ponds can be problematic if the algae is heavy to start with.

And here’s one final point I would like to make.  When I say “algaecide” I’m specifically talking about a group of products that are designed to kill algae very quickly.  It doesn’t matter what make or brand they are or whether they contain copper sulphate or are a contact product like the Green Clean that we carry in our store.  The reality is that since they can kill algae quickly, they all carry a risk of harming fish indirectly if they are mis-applied.  And many of these products will not warn you of this on the label so it’s important to know the facts before you apply them to your pond.

Algaecides are not and never will be my preferred choice of treating algae problems.  It’s safe to say as well they surely are not my first line of defense.  Yet they do have their usefulness and can be helpful in certain situations, as long as they are applied in a way that minimizes their effect on the pond as a whole, yet directly targets the algae in a measurable way to retard it’s growth.

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