How to convert a koi pool or pond for fish farming

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There are many ways to keep fish in your backyard. You can use an existing lake on your property or install a complex reservoir system. Or, you can convert an existing pool or koi pond into a pond for fish farming.

If you are new to fish farming, check out our full introduction first. This will help you understand how to start the process.

Then come back here and we’ll help you turn that unused pond or pool into a working fish farm.


How to convert a swimming pool

Whether you have an existing in-ground or above-ground pool that you aren’t using, you can convert either into a fish pond. Here’s how to convert a swimming pool into a fish farm:

1. Prepare a swimming pool

If you have an in-ground swimming pool (first, you’re in luck!) that you’re tired of maintaining, converting it to a fish pond might be a good option for you.

If you don’t have an inground pool, you can always buy an above ground pool. Depending on the time of year, you may be able to get a lot out of it. You can buy a good above ground pool in a variety of sizes here.

Or check local marketplaces like Craigslist or Facebook to see if anyone else is looking to get rid of theirs. Many people find that their pools cost a lot more to run than expected and would like to get rid of them.

Then configure everything so you can move on to the next step. If you have a pool that you have neglected for a few years, be sure to clean and scrub it well. If your pool is currently operating, turn off all equipment and stop adding chemicals.

You want the pool to be a clean slate before you start dumping your fish in it.

2. Add water and start building your ecosystem

Fill the pool with water. This can take a long time, depending on the size of your pool, so start early and plan to stay long. Completely fill the pool and let it sit for 7-10 days.

You want the chlorine or any other additives to evaporate before you start adding your fish. You also want mud, silt, or dirt to settle on the bottom of the pool, as dirty water can make some fish sick. In fact, fish like trout or salmon could die.

3. Provide filtration

There are three types of filters: biological, mechanical and water clarifiers. Because your pool is a closed system, you will need some sort of filtration to have a healthy fish pond.

It can be as simple as a pump that pulls water through fine rock or as complex as a pond skimmer combined with a mechanical filter and a biological filter.

A skimmer vacuums debris from the bottom of your pond, while a mechanical filter traps debris. A biological filter uses bacteria to break down waste. The better your filtration, the happier most fish will be.

There are exceptions, such as catfish, but most fish need good filtration. Trout and salmon, in particular, need clean water.

You can’t just reuse your existing pool filter, it’s not equipped to handle the unique environment of a pond.

4. Add aquatic plants

After the water has stood still for at least a week, you can add floating or submerged plants. Water hyacinth, iris, taro, water chestnuts, floating fern, frogtail, water lettuce, parrot’s feather, anacharis, and hornwort are great options.

Our guide has many other species to consider. Ultimately, you want a ton of plants. At least half of the water surface should be covered with plants. Don’t forget to transform these stairs into a marginal plant environment.

Some of the waste produced by your fish can be cleaned up naturally by plants.

Some people raise plants in galvanized tanks with gravel at the bottom, then pump the clean water into the living area to give the fish better living conditions. Healthier fish means a more nutritious food source for you.

If you opt for the tub, insert a pond pump that will allow the filtered water from the plants to flow back into the pool.

5. Feed the fish

Plants provide natural food for your fish. Also, once the water is healthy, mosquitoes will start laying eggs in the water, which is another food source for fish.

Honestly, if you’re looking for an easy way to keep fish, you might prefer to feed them store-bought food.

However, if you are looking to be completely self-sufficient, then in the long run, taking the time and effort to build your own healthy ecosystem will be your best path.

It’s really about your goals. Just be sure not to add any chemicals to the water.

We could go on and on about building a healthy ecosystem for your fish, but this will get you started.

How to Convert a Koi Pond into a Fish Farm

I love Koi ponds. I think they are pretty to look at and add a nice touch to an outdoor space. Even so, if you’re like me, if I have something on my property (nice or not), it must be of some use.

Why not use your koi pond as a fish farm? Here’s how:

1. Prepare a Koi Pond

If you have an existing koi pond, you’re set. Just clean it to get it ready for its new job.

You can buy koi ponds of different sizes at most home and garden stores or you can also buy them online. For example, you can purchase a 400 gallon koi pond here. It even includes lights so you can enjoy the show at night.

You need to consider the number of fish you want to keep before buying. You would hate to have a koi pond that was too small.

It would be just as frustrating if you bought a large koi pond and didn’t use it to its full potential.

Try to come up with a ballpark figure for how many fish you would actually like to keep, then choose a pond. The rule of thumb is one pound of fish per five gallons of water.

2. Add water

As for the swimming pool, it is necessary to add water. Again, make sure you don’t add chlorine or anything chemical to it. Let the water sit for at least a week before adding the fish.

There are chemicals you can buy that are supposed to keep algae away. Even so, if you form a natural ecosystem, a small algae is a good thing.

What you do or don’t use in your koi pond will depend on whether you’re trying to go all natural with a DIY ecosystem or not.

3. Develop the ecosystem

As with the pool, add plants and let the ecosystem grow. You will also need a filtering system.

If you want to keep it natural, you can place plants and stones in galvanized tubs and then pump water through them. Pump the clean water back into the pool.

Or you can opt for a more complex filter system as described above.

Don’t worry about adding decorative stones or waterfalls.

Remember, this is about developing a self-sustaining ecosystem so you can keep fish, not providing an ornamental element to your garden. It can certainly serve both purposes, but the purpose is the function.

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