Rain can help your pond by providing a free, gentle water source that is free of pollutants such as chlorine and chloramine. This “free” resource may not contain dangerous chemicals, yet it poses numerous risks to your pond. Rainwater quality varies by geography, with heavily industrialized areas releasing more toxins into the air and water.
Leaves, fertilizer, and other surface runoff will harm your pond’s pH levels by obstructing sunlight, disrupting chemical compounds, and ultimately creating an unsafe habitat for your inhabitants.
So now the ultimate question that needs to be answered is, Is rainwater good for pond fish?
The answer is a big No!!
It’s now quite obvious because of the fact that acidic rain isn’t ideal for aquatic animals to survive. It is not advisable to use rainwater in an acidic pond because it can soon become toxic to your fish.
There are filtering systems in place to eliminate any toxins that remain. Install a cover around the perimeter of the pond to keep rainwater out of the fish pond. Though It’s tempting to collect and store rainwater, it’s not a good idea and isn’t advisable.
Make sure to keep your pond clean by removing algae, leaves, and other debris that may fall into it after rain.
Now, this brings us to the next question.
Why is rainwater not good for pond fish?
Despite its ominous name, acid rain is only a mixture of wet and dry deposited particles (nitric and sulfuric acid). It technically refers to any type of precipitation with a pH value less than 7, making it dangerous for fish to live, or any other aquatic animal for that matter inside the pond.
The overall concentration of hydrogen ions in a given sample of water is what the pH system boils down to, with each lowering value reflecting a tenfold increase in concentration. A pH of 4 has ten times the hydrogen ion concentration of a pH of 5 and one hundred times the concentration of a pH of 6.
Below are some of the main reasons explained in detail as to why rainwater is not good for pond fish.
1) Rainfall changes the chemistry of the water.
Because of the nature of the water cycle, rainfall is often high in nutrients. Most water will move through the soil, plants, the bodies of animals that absorb it, and the atmosphere during the cycle. Rainwater, as a result, often contains sodium, phosphorus, calcium, magnesium, nitrogen (mainly from passing through the atmosphere), potassium, as well as other toxins present in the soil or atmosphere.
Gardeners normally like rain for their plants because of these nutrients, but when it comes to ponds and other water bodies, too much rain can release too many nutrients too rapidly, overwhelming the system before it can filter them out, changing pH and water hardness, and inflicting fish kills. Sudden pH fluctuations, for example, might deplete the protective mucous layer that covers fish gills, leaving them prone to disease, lesions, and parasites.
2) Turnover Is Caused by Heavy Rainfall.
Warmer, oxygen-rich water is found at the water’s surface during the summer and early fall, whereas cooler, anoxic waters with less oxygen are found at the bottom of deeper water bodies such as lakes and larger ponds. Rain is typically cool or cold, with cold water being heavier than warm water. When a storm dumps a large amount of cold, dense water into your pond, it settles to the bottom, displacing the low-oxygen water at the bottom and driving it to rise to the top, where fish usually live.
Besides the fact that the water temperature has suddenly changed, which can cause paralysis or even death in fish, the fish are now surrounded by water that lacks oxygen. Many fish die due to suffocation after rainstorms. Even if there is no rain, a strong wind can cause this dangerous turnover. Sudden turnover also stirs up debris, resulting in hazy water that is difficult for your fish to swim in.
3) Rainfall has the potential to physically wash fish away.
Flooding would inevitably occur if too much rain falls too soon, as the earth will be unable to absorb all of the moisture. As a result, severe rains can occasionally flood your pond, washing your fish out. If this occurs while you are around, great!! You may be able to capture your fish and keep them indoors in containers or tanks. If you’re away during a storm and this happens, it’s not rare to see fish washed up on the land after a heavy downpour, which, of course, kills them if they can’t get back into the water within a few hours.
4) Heavy Rain showers Lead to Runoff.
This one is a bit of a tie-in between flooding and water chemistry. Water will run downslope after a heavy rainstorm because the earth will not be able to absorb it all quickly enough. As water flows across the ground, it picks up a variety of nutrients and contaminants, which are eventually deposited wherever the water stops flowing, such as in your pond.
If you live near an agricultural area (the primary concern is manure from cattle as well as fertilizers), an industrial location, or in/near a city where water might pick up a variety of pollutants, this is very concerning (such as leaked motor oil from cars). All of these extra nutrients and chemicals will change pH, reduce oxygen, and feed potentially toxic algae, potentially resulting in suffocation and fish death.
How to protect pond fish from rainwater?
Below are some of the best ways to protect pond fish from rainwater.
1) Maintain constant aeration and oxygen levels.
After heavy rains, an aerator keeps ponds clean. Though installing aerators in your pond won’t completely prevent the risks associated with heavy rains, it will help to ensure that oxygen levels remain stable in the event of a turnover.
Install at least one aerator as well as plenty of plants to help oxygenate the water if you don’t already have them. A small waterfall, air pump, or fountain can help keep water mixed up and aerated, minimizing the effects of any turnover occurrence that may occur (as long as the water movement isn’t too fast or choppy, as pond fish prefer still waters), so having one can help provide dissolved oxygen (as long as the water movement isn’t too fast or choppy, as pond fish prefer still waters).
2) Prepare strong Barriers and Fencing.
During severe rains, fish could be protected by fencing and barriers.
This one may seem unusual, but fencing your fish is a really simple and uncomplicated approach to help safeguard them. If the pond floods, the fence will keep the animals inside the pond and away from your property.
Alternatively, you might raise the pond’s rim several inches above the ground, which would help prevent material such as dirt, grass clippings, and trash from flowing in, as well as preventing your fish from being washed out.
3) Drainage or Overflows should be installed.
Fish are protected from severe rainfall by a runoff skimmer mechanism.
You can install a drainage or runoff system to keep water levels stable during heavy rains. Install a genuine drain (such as a grate with rocks) at a low location near your pond or at a high height on a pond wall to do this.
Another alternative is to aerate your soil by poking small holes in it (like farmers do in their fields) so that it can absorb water more easily, or to create your own mini-wetland area right outside your pond. Wetlands are nature’s purifying sponges, soaking up and effectively filtering water and nutrients. Alternatively, a pond skimmer placed just above the water line and connected to a drainage pipe should serve to remove extra water and debris.
You should also include a slope on at least one side of your pond to allow excess water to drain and prevent floods. Depending on which side of the hill your fish are on, you may want to install fencing to keep them from getting washed out. In a similar fashion, if you’re going to build a pond, make sure it’s at the highest point on your land to avoid flooding.
4) Lower the total bioload in the pond
After the rain, the pond filtration system minimizes the bioload by removing too many nutrients.
Limiting fertilizer use near your pond (as well as any chemicals in or around your pond), avoiding trimming grass within a meter or so of your pond’s edge, and collecting leaves and sticks from your yard on a regular basis will reduce the amount of waste that washes into your pond during heavy rainfall.
Furthermore, you need to establish a filter system that is enough for your fish stocks and is cleaned and maintained to a high standard on a regular basis. As a result, all of these techniques reduce the possibility of overloading your pond and changing the water quality beyond what your fish can tolerate.