Pool shock in a pond? Here’s what you must know


Taking care of a pond is time-consuming, and not to mention, there are about a million things to remember while caring for your plants, fish, fountain, and more. While trying to keep it clean, you might wonder, “Can’t I just shock my pond with chlorine?”

Using pool shock is an effective way to clean a pool, but it should NEVER be used in a pond. “Shocking” is the process of exposing water to a concentrated amount of chlorine all at once, and nothing will survive. Alternate water treatments can be used in a pond to discourage algae growth.

Ponds are pretty, algae is not. When algae overruns your pond, it almost ruins the point of getting a beautiful pond in the first place. It makes sense that you want it out of your pond as fast as possible, but other methods are much better at ridding yourself of algae without harming any of the plants or fish.

What is Algae? (And what does it do?)

Everyone knows about algae. It is a form of aquatic plant life without any roots, stems, or leaves, but algae can also be found on land in plenty of places, as long as those places are wet.

Algae can grow anywhere. As long as there is enough water, (freshwater, wastewater, seawater, it doesn’t matter) and sunlight, algae can be counted on to show up where it’s not wanted. Just like that person you went on a date with once (who won’t stop texting you), algae can’t take a hint.

In small doses, algae can be a productive member of an ecosystem. It can serve as food for most pond fish. The problem, as I’m sure you know, is that excessive algae will also crowd out other plants and fish in your pond.

Unfortunately for the rest of the organisms in your pond, the algae will spread across the surface, not only blocking any oxygen from dissolving into the water, but also blocking sunlight from getting to other plants and animals.

This is what’s called a dead zone because when algae growth goes too far, nothing else will be able to survive. The oxygen levels will be far too low, and since no sunlight can get to the other organisms, it’s not a question of “if” they will die, but “when?”

It’s natural to look to chlorine as a remedy for such a dire situation–after all, algae is sucking all the life out of your pond, like a slow, mucky parasite. But while chlorine has its place among stinky water parks and swimming pools, the last place it should be is in your pond.

Pool Shock: Good and Bad Chlorine

Pool shocking is something that people talk about all the time, but the real question is, what is it, and how does it actually disinfect bodies of water?

Well, pool shock, unsurprisingly, is made up of chlorine (either in powdered or liquid form) and is used when pools start turning green or smelling like a lake. This is because algae likes to pop up in any body of water it can find, and pool shock keeps it away.

Pool shock does this because it is made up of free chlorine. Free chlorine is pure chlorine that hasn’t combined with any ammonia chemicals, and therefore, it is able to effectively disinfect pools.

But what about chlorine that combines with ammonia particles? When free chlorine bonds with ammonia compounds, they create chloramines, or combined chlorine.

Free Chlorine + Ammonia = Chloramines (Combined Chlorine)

Combined chlorine is not an effective disinfectant. In fact, combined chlorine acts as yet another chemical to make pools even dirtier.

If you know anything about swimming pools, you know that pools usually have a steady stream of chlorine being pumped into the water, just to keep most bacteria at bay. However, the fact that chlorine combines with ammonia means that the steady chlorine will turn into combined chlorine; becoming part of the problem.

It doesn’t just fail at disinfecting the pool, but algae can also feed on some types of combined chlorine.

This is why shocking pools is so important. Shocking a pool doesn’t just mean adding a little bit of chlorine every once in a while to kill some unwanted microorganisms.

Shocking means SHOCKINGfilling the pool with enough chlorine to pass the breakpoint dosage and eliminate ALL bacterial colonies, algae, and chloramines in sight! Thirty ppm (parts per million) is the minimum amount of chlorine needed to effectively shock a pool (without just feeding the algae even more).

Chlorine in Ponds (Side Effects)

The effects of using chlorine in your pond are pretty self-explanatory. Chlorine is toxic to any form of life in high dosages, and it has a number of effects on plants and fish that live in ponds.

Sometimes it can be harder to tell if your fish are being negatively impacted by chlorine, but chlorine in the water will stress out your fish. It might be hard to imagine stressed-out fish, but they are living creatures, and just like us, they have the tendency to stress out when put in unhealthy environments or conditions.

But chlorine can do worse than just mess with fish psychology. The reason that the koi fish get stressed out is because the chlorine removes a natural slime coat on their body–a slime coat that protects them from deadly bacteria. When koi fish lose this coat, they’re much more likely to get deadly disease or ulcers. The amount of chlorine needed to shock a pond is more than enough to kill every single fish.

While low levels of chlorine are necessary for plant growth, high amounts of chlorine will be toxic to them. Plants are more hardy than fish and can stand larger levels of chlorine for longer, but they will start to look scorched and withered. And shocking a pond will saturate the water with more than enough chlorine to wipe out every single leaf.

You could try to just integrate low levels of chlorine into your pond, instead of shocking it outright, which would be better than shocking. However, as mentioned before, chlorine in small dosages will bond with ammonia particles and form chloramines, which will make the algae problem even worse.

The best way to get rid of algae in your pond (if you want to keep everything else alive) is to avoid chlorine completely.

Alternatives: The Better Options

Even though chlorine is not an option for algae removal, there are plenty of other ways to eliminate or prevent algae from overtaking your pond. While some forms of algae are easy to pull out or wipe off by hand, a lot of algae is the single-celled kind that just floats through the water aimlessly and turns the entire pond green.

First things first, there are other chemicals that are made and sold purely for the purpose of getting rid of algae, and unlike chlorine, these products are made with the knowledge that they will come into direct contact with fishes and other plants. The most common one is called “Algae Control.”

However, you should be careful when using this product for your pond. There are many cases where this chemical also killed all the fish. In order for this to work, you must use only one drop of it per gallon. When this is used properly, it can clear algae out of a pond within twenty-four hours.

If you don’t want to use any chemicals in your pond at all (accidental fish genocide might put a damper on one’s day), I don’t blame you. And don’t worry; there are plenty of other options for getting rid of algae that don’t involve man-made chemicals.

Algae thrive in conditions with lots of moisture and lots of sun, so a good way to get some more shade over the surface of your pond is by adding more pond plants to the water. Not only will these plants block out the sun, but they are in direct competition with the algae for nutrients. More pond plants mean fewer nutrients in the water for algae to feed on and less algae growth.

If your pond doesn’t have fish, you might want to consider getting some. Fish are a great addition to any pond, and if you do the proper research, you can find the right fish for your pond. Fish are beautiful, colorful creatures and algae is a huge part of their diet.

If you already have fish, consider buying high-quality fish food. Higher quality fish food will be mostly digested by the fish, so the fish waste will have fewer nutrients for excess algae to feed on. Keeping from overfeeding your fish should also help with this problem for the same reason. Less waste=less algae.

Another option is to add an Ultraviolet Clarifier to your pond. These are self-contained devices that filter the green water through UV light, which will effectively kill the excess algae floating in the water. This option can cost around one-hundred dollars, but it’s an effective way to rid yourself of algae if none of the other preventative methods work.

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