A pond algae question

[Henro]

My pond is not large. Probably around 80 x 50‘ and not deep. At one point the deepest part was about 5 feet and the rest was tapering up to about 2 feet maybe. But over the years it got silted in, so it’s even shallower now.

Anyway, it used to have a lot of algae from spring to fall and had a green color to it, which I didn’t mind because I couldn’t see the bottom and it gave the illusion that the pond was deeper. I think the lack of clearness due to the allergy also helped the goldfish hide from predators, and perhaps offered them some food even. I’m not sure about that.

So last year I ended up with a leak that drained the pond almost totally, but not completely. I know why that happened, but I’m not going to get into the reason here cause it’s not relevant to my question.

As part of patching the leak, I ended up getting a certain amount of cement into the water of the pond. Actually, it was concrete mix, and not cement, but cement is part of the make up of concrete mix.

What I noticed this year now is that the algae is not there anymore. The pond is still clear, even though it’s a hotter than average summer, which is extremely unusual as far as the pond algae goes.

So what’s up with the lack of algae? And what do I do to get it back? I know this is the opposite of what most people want! When I had algae I wished I didn’t, but now that I don’t have it, I wish it was back

 

[OntheRidge]

Total WAG, but I would say the lime from the concrete mix is why, changes ph of water or some other magic.

 

[NCL4701]

Was typing at same time as @OntheRidge and second his thoughts.

Algae tends to like pH in the 8.0 +/- area. Of course that varies a bit depending on exact type of algae and some is pickier than others. Quite possible the cement was enough to change the pH to something outside the threshold for growing whatever kind of algae you had. I would start by checking the pH level in your pond. Could be other issues, I suppose, but that would be my first thing to check.

 

[Henro]

Was typing at same time as @OntheRidge and second his thoughts.

Algae tends to like pH in the 8.0 +/- area. Of course that varies a bit depending on exact type of algae and some is pickier than others. Quite possible the cement was enough to change the pH to something outside the threshold for growing whatever kind of algae you had. I would start by checking the pH level in your pond. Could be other issues, I suppose, but that would be my first thing to check.

A good point. Thanks to you both!

I forgot to mention that the pond is spring fed and my guess is even when the weather is dry, it probably has an about a weekly water change. Could be two weeks maybe. Would the lime remain there and have an effect on ph after the concrete that was exposed to the water cured? No background in chemistry or whatever’s related to it here at all!

 

[Henro]

So thinking about it, only two things have changed over the last 20 years. One is that the pond got drained about 90%, and it stayed that way for several weeks. I can’t remember how long but it wasn’t real quick before I had that leak fixed.

The other is the exposure of the water in the pond to the concrete mix that was purchased in bags.

I don’t think anything else changed or was new.

If I think of anything else I’ll be sure to list it in this thread. But I really doubt there’s anything else.

edit: I’ve also noticed less frogs. We used to have a lot more bullfrogs. Spring that feeds the pond is a shallow spring. In the past, when I measured it when the water level in the ground was high it would flow maybe 5 gallons per minute. During a drought, it might get down to a half gallon a minute. Right now I think the average flow is probably about a gallon a minute, but could be less.

 

[skeets]

Maybe when you mow,, blow the clippings in to the pond, that might lower the Ph some and what ever little critters on the grass might take hold.. just a WAG

 

[jaxs]

I'd count my blessings and put floating plants like lily pads in it. Oxygenates water and attracts creatures to feed fish and frogs.

 

[X-Pup]

There needs to be a balance of bacteria for a good ecosystem that attract frogs and such.

Normally one would add what is considered beneficial bacteria to keep the pond from turning green. Although just because a pond is green, doesn't mean it's out of balance - you just can't see the fish.

More fish waste will get it back to more of the green effect.

Usually, I would seed the biofilter in the spring each year. But in your case, since you rely on a continuous freshwater feed, you would need to somehow seed the pond itself. They sell bacteria for both.

I'm no expert but I did raise Koi for a few years.

There used to be a lot more pond stores around that could sell you the bacteria you need. But you could always just add more fish. And lilies are a good idea. Keep in mind though, lilies can be invasive and hard to get rid of. Frogs and fish really like them though, and you get pretty blooms. If you get a native species they will come back on their own year after year.

As was suggested earlier, knowing your PH can tell you if there's a real imbalance. There are treatments/chemicals that can bring it back in balance. It's been too long, so I don't remember what the target PH is but it's not hard to google it.