Algae, Duckweed and our Ponds

Several people on Instagram, in text messages and in-person have raised concerns about algae in our ponds where the dogs (and people) swim. Right now 1) we have essentially no algae and 2) algae is nothing like duckweed, which we do have.

Duckweed is a plant. Algae isn’t. An individual duckweed plant is visible to the naked eye. Algae (singular form?) is microscopic. They are both in water and green, but beyond that, they aren’t even close! Not even the same kingdom!

I saw an award-winning video on Khan academy that mixed up algae and duckweed – which is worse than mixing up an oak tree and a blade of grass – but they still gave out a SCIENCE award.

Let me refer to you a source that is dutifully scientific and neutral in tone. If you look at that link, you can see the different kinds of conditions that may be dangerous in ponds. Look at the pictures carefully and then go check out the pictures on our site of the dogs swimming. The only condition listed on the DEC page that we have is duckweed. The page says, “Although duckweed can cover the water surface, it is not algae, and does not produce harmful toxins. It is a tiny aquatic plant with a grainy texture and looks like a miniature lilypad.”

Here is what the DEC told me in an email, “We do not recommend testing waters for HABs… HABs tend to be localized, and we have good evidence that water that is clear of blooms, discoloration, and scums for at least a day is not likely to contain residual toxin.”

We check the pond every day according to the DEC recommendations and no pond here has ever had “blooms, discoloration, and scums”. If we see anything suspicious, we will stay out and report the condition to the DEC.

Duckweed is not algae at all! Not even close! The water in our pond is crystal clear – before the dogs get in and stir up the mud. Below the duckweed, it’s clear and free of green color indicating high quantities of algae.

Blue-green algae are buoyant, and most other algae aren’t. You collect a water sample in a shallow spot, then you put a lid on the cop and Shake It. You leave it overnight, and the next day you see if algae have collected at the top of the cup or at the bottom. If it’s collected at the top of the top, there’s a pretty good chance it’s blue-green algae.

DEC page with photos and videos is excellent: toxic algae are not going to sneak up on you. We monitor for visual evidence of algae. Duckweed may actually help keep the water cooler on a sunny day and reduce the chance of algae.

Also, there is a test for the toxins produced by the algae but there is no test for the algae itself. You can see the algae in the water. If someone tells you they are testing the water, that sounds dangerous. True, you can have the algae and no toxins but if you have the algae toxins can appear for a few hours and then disappear. Testing might give you a false sense of security. So, the DEC doesn’t recommend water testing for HAB.

Now, duckweed is annoying to swim in (although the dogs don’t seem to care) and doesn’t look good in pictures. The environmentally correct solution to duckweed is grass carp. Here is the permit application. I did that. Here is the fish farm where I went to buy nine carp, as per my permit. They all died in a harsh winter (ice builds up and they run out of oxygen). So, I dug a trench from my house to the pond and installed an aerator from this supplier.

When you put in an aeration system, equipment designed for septic systems work well, as shit at the bottom of a tank and mud at the bottom of a pond operate in a similar way in term of clogging and interference. Also, put your open water area near the edge of the pond, not the middle, so if someone falls in, such as an animal or child, you can easily access the area and pull them out. Mark the area well for all humans on the ice and fence the area off for animals so they don’t go skating and weeee! plop! noooo!

I love Septic Solutions and I love Northeast Aquatics. Both great.

Now the fish should be able to survive any winter, as the bubbles (like in a fish tank in your house) will keep oxygen in the water, open water all winter. I just have to go back to Rhinebeck and restock the pond, nine more grass carp. That would take three hours. I can’t really send anyone and I personally have not had time.

Grass carp are from Siberia originally and voracious eaters of any water plant. The state allows their sale – only males, and all sterilized at a place in Kentucky or somewhere around there. This prevents them getting in the local water bodies and eating all the endangered native vegetation.

They are from Siberia originally but still die in an upstate New York winter when they are in a POND. In their native environment, they are in streams and rivers, which move, and oxygen is not a problem in the winter. Obviously, a creature from Siberia is not affected by the cold. It’s the circulation of oxygen that is the issues.

There is a flaw with the state system to keep carp out of New York waterways: there already are grass carp in the Hudson and in the Kinderhook Creek. The way you can catch a grass card to eat (or illegally put in a pond where they do not exist already, which would be illegal and ill-advised) is to bait a small hook with a kernel of corn. As carp are grazers, like a cow, and not hunters, they have to more or less swallow the hook before you pull up on the line. If they notice the hook in the corn, they’ll just spit it out and move on. It’s much easier to catch predatory fish with a hook than more vegetarian species, for this reason. However, carp like anything sweet, like corn. If you don’t pull to soon, get one that isn’t too big, you can remove the hook later and have a live carp to eat your duckweed, but that would be against the law and would take a lot more time than I have. If I don’t have three hours to go to Rhinebeck with 9 x $15 I’m not going to catch some grass carp from the Hudson. If you do have time and the right hooks, however, text me and I’ll spring for the can of corn.

This blog post may include more details about pond management than you needed unless you want to build a pond, in which case it’s not enough information.