Putting Fish in a Swimming Pool : 12 Tips to Consider

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Attractive pool with fish in it.

This article has been authored by the owners of this site. No input or information has been generated by any AI systems.

We are like many families where the kids have grown and left home to make their way in life, leaving an unused swimming pool in the yard. We didn’t consider filling it in and didn’t like the chemicals.

This was in 2015, and we had just completed a PDC (Permaculture Design Certificate) and had been introduced to aquaculture. We decided it made sense to put Fish in the pool, so we did.

We learned a lot during this process, and this article is here to share what we can.

The costs associated with running a pool can be high, and if the pool is not being used as a swimming pool, it is only logical that thoughts lead to the question of what to do with the pool. Some people fill the pool back in and plant gardens or lawns over the top.

Others cannot bear to see the money that went into digging the pool get covered with soil and lawn.

An alternative that is getting some attention for the unused pools is putting Fish in them, and while this sounds like a fun thing to do, there are a few things to consider before you throw the Fish in.

We have been down this path here at Self-sufficient Home Life, and maybe you can find some information in this post to help guide your choice on what direction to take.

How hard is it to keep Fish in a pool?

Keeping Fish in a pool is challenging, but it is not hard. Here’s a list of things to consider before you take the plunge.

  1. Aesthetics.
  2. Community considerations.
  3. Property size.
  4. What type of Fish.
  5. Fish Lifespan.
  6. Water quality.
  7. Pool construction.
  8. Pool size.
  9. Fish food.
  10. Pet or protein.
  11. Aquaculture vs aquaponics.
  12. Stand-alone or part of a system.

Is keeping Fish in a pool messy?

Keeping it all looking good is important. The process of having Fish in your pool can be messy if you let it become that way. Backyard aquaculture can be accomplished attractively.

Not surprisingly, this is a huge topic because Fish thrive in a natural setting with a supportive ecosystem where the Fish are just one part, and beauty can mean different things to people.

A bare swimming pool does not look anything like a natural setting. It is a barren, lifeless hole with sterile liquid that cannot support life, often surrounded by landscaping.

This is deliberate for the swimming pool owner because once the life moves in, the pool turns green and before you know it, there are frogs, birds, and a myriad of insects all getting along in your pool.

So the typical pool owner keeps up a regimen of chemicals and treatments to keep that water sparkling, and for a good reason.

A well maintained pool can look fantastic and very inviting to us humans.

If Fish are to be introduced into a pool, it is necessary to change the way you look at the pool.

You must realize that natural systems are not always pristine and photogenic, and the path of converting a pool to a biological system can become a little out of your control…depending on the desired outcome you have in mind before you begin.

fish in a backyard swimming pool
This pool holds 250 Jade Perch fingerlings. Grow-beds as filtration while the fish are small.

Will pool water smell if Fish are in it?

The water quality is correlated with how you approach putting fish in it. Well aerated water with Fish in it has no smell.

What will the Neighbors think?

The neighbors need not even know there are Fish in the pool.

This all depends on where you live and the makeup of your community.

People in smaller towns think differently than city folk, and gauging the people closest to your property can be a start before you set off on your journey to convert a pool to a fishpond.

If you have a large block of land, you have less to be concerned about than someone in an urban setting with close neighbors all around.

Ultimately, it is your pool and your property, so as long as local regulations are followed, you should be fine to convert it.

What other people think should be given a thought, but it should not be the deciding factor.

Property size Matters.

For simplicity, I will split this into just two types of property. Rural-residential and urban-residential.

Rural residential.

I will assume that most properties in this category are large, and this opens up the choices you have regarding how to approach putting Fish in the pool.

I am only talking about man made swimming pools here and not a natural pond setting.

Due to having the extra space to do things and get creative, you can have a few Fish only as a hobby setup, or you can stock the pool with Fish and use the pool as a source of protein supply.

Each choice comes with setup criteria you might want to explore before committing to further action. The important thing is to do all the planning before committing.

Urban residential.

This setting is more restrictive depending on your location and block of land, but it is safe to say that you have more limitations than someone in a rural setting.

These limitations revolve around the many by-products that having Fish in a pool creates because it can be noisy with pumps and aeration systems running.

There is waste generated (read fish poo) with more Fish, and this needs to be addressed on-site, but it need not be a problem. This is an opportunity to harvest nutrients.

Your local governing body will likely have guidelines of what you can release onto the street or wastewater system, so keep within the guidelines, and all should be sweet. We retained all nutrients and used them on gardens.

The hobby approach is more suited to the urban setting because of the waste issues. Everything can be scaled back when just a couple of Fish are involved, and the pool can be kept relatively clean and presentable.

The koi Fish keepers are evidence of this.

What Type of Fish do I put in my Pool?

This is such a big question that we will put up an entire post just on this topic alone.

However, this question is already half answered by you when you understand where you live, the size of your block, the level of aesthetic appeal that is important to you, and the reason you wish to put the Fish in the pool first place.

Will the Fish be pets or destined for the dinner plate? We approached it from the dinner plate perspective, and this post here details our problems along the path.

jade perch fingerling at 4 months old
These fingerlings have been in the pool for about 3 months and eat mango.

How Long do Fish Live in a Backyard Pool?

Our experience is at least 5-6 years, but this is for a Fish breed known as Jade Perch or Barcoo Grunter.

It is a native from the Barcoo River system in western Queensland, Australia, and is well suited for aquaculture processes.

There is a ready market for farmed Fish with this species, which tolerates a broad range of water conditions. It was perfect for what we wanted to achieve.

Typical lifespans of popular Fish types.

  • Koi can live longer than 20 years
  • Goldfish can live for over ten years
  • Tilipia up to 13 years
  • Perch very variable. 5-25 years depending on breed and conditions.

I suggest researching Fish for your country and climate first as a starting point because, as with so many questions asked, the answer to the “how long do they live “question is “it depends.”

It depends on your location first of all. Climate and temperature variations will restrict your choice of species and your access to quality water.

The size of your pool matters. Large bodies of water buffer temperature swings that can harm some Fish breeds.

What Type of Water do Fish Need in a Swimming Pool.

This should be simple to understand but some folk still try things that are destined to fail. The best water for Fish in a swimming pool is fresh water.

If you are wondering about salt water fish in your pool you are making far more work for yourself and making it far more likely the project will fail.

Saltwater Fish require a water quality close to the ocean’s quality, and there is a massive difference between your pool and the ocean, not just in size but in the ability to filter and aerate the water.

Oceans are living ecosystems, and you want to replicate that in your backyard pool? I recommend putting the saltwater Fish in a closely monitored indoor tank, not a pool.

Fresh water is the easiest water to work with; however, it comes with its challenges. Keeping it filtered and aerated are the primary concern here.

This is helped or hindered by the number of Fish you put in the pool, to begin with, and there is more on that below.

water quality is vital to keep fish healthy. Image shows clean water returning to pool from groabeds.

What type of Swimming Pool is Best For Keeping Fish?

This is connected to the question above in a way. The most popular pool types are concrete and fiberglass.

Each has its benefits, but the concrete pool has a hidden danger for water quality. Depending on the age of the pool, the pool shell can leach lime and calcium into the water, which can alter the water chemistry without you knowing.

It is important to keep a water testing kit that can measure total alkalinity as well as other things like pH, ammonia, nitrites-nitrates, and others.

The importance of a testing kit is dependent on how many fish you have in the pool. A lot of fish will change the water chemistry far quicker than just a few Fish and can spiral into trouble fast in some situations. The fiberglass pool has no leaching issues that I am aware of.

Water testing should be done no matter what type of pool is used but be aware of the leaching behavior of the concrete-shelled swimming pool.

What Size Pool Works best for keeping Fish?

No one size is best, and your pool will be suitable if it is at least 10000 liters or about 2000 gallons.

The more water there is, the better. It helps stabilize the water for temperature movement, water chemistry, and general space for the Fish to move about.

Much of our discussion depends on what you want to do with the Fish. If they are for the plate, then everything scales up according to pool size and should be driven by biomass to pool volume.

In this case, everything scales, including filtration, aeration, waste management, evaporation, and more. Monitoring the water quality is paramount if there are lots of Fish.

What Food Do Fish Eat in a Pool.

This depends on the species you choose. There are two types of Fish feeding behavior, one being herbivorous and the other predatory.

Some species are both. The Jade Perch we had in our pool are both, or omnivorous. We could give them pieces of fruit like mango or papaya, and they would love it.

They would also eat insects at times but had definite tendencies towards herbivorous behavior the older they became.

The type of food you give them can vary a lot, with many commercial feeds having ingredients containing fats, oils, and processed animal bits. It is important to ensure all of this type of food is eaten, as the ingredients can turn a small body of water sour if not watched.

Others have quantities of wild-caught Fish processed into the food, primarily pellets or flakes. Your choice will come down to the Fish species, how environmentally concerned you are, and the food availability.

We grew a large portion of the Fish food on our block with just rolled oats as the added extras. It was reasonably efficient and very cost-effective. Sustainable fish food article here.

Can Fish Become Pets in a Pool?

Fish can become pets when kept in a pool. Some Koi have been known to be with their owners/keepers for over 25 years and become attached and very habitual.

The pet approach is well suited to the urban hobby aspect, as we mentioned at the beginning of the article. It is also applicable in the rural aspect, and the tendency toward larger pools in the rural setting allows for several to many Fish in the pool.

Making the Fish pets is one side of the question for the person thinking about how many to put in.

The other side of the question is growing them as food. Do they or will they turn into pets, and will you have trouble harvesting them when the time comes?

This should be discussed before you put any in the pool because it will have a bearing on the Fish species and the timeline you have them in the pool.

Are you growing for food in a self-sufficient system, or is it just a reason for not filling in the pool?

Aquaculture or Aquaponics, which is best for a backyard pool?

You might approach this from the angle of how involved you want to be.

The Aquaculture setting is based around Fish farming, which will rule out the residential pool owner, generally speaking.

The rural pool owner can approach from this angle if the pool is large enough to make it viable.

Something to consider here is that the more Fish you have in the pool (as you are farming them, this makes sense), the more equipment and knowledge is required to keep the system stable.

Larger filtration units and aerators. It becomes more intense.

Aquaponics, on the other hand, connects Fish and plants through water flow and natural filtration methods.

There is plenty on the net detailing the different setups and requirements, but we have personal experience in growing vegetables from the Fish’s waste, and this is what we know.

It is a system that requires you to have a basic understanding of water chemistry to have the system operate at a practical level for both fish and plants. This practice is often designed with harvesting the Fish at some point, so consider this before jumping in.

It is a dynamic process where the waste must be controlled through plant growth, and as the Fish gain size, the nutrient loads rise and can create problems if not monitored appropriately.

Another method that has been gaining traction is what is called “natural” swimming pools. This method plugs a wetland habitat to the side of a swimming pool, and the plants filter the water.

They can be very attractive and may suit your situation, but only on a larger block of land.

grow beds on the side of the swimming pool.
Scoria as a growing media worked well with plants that had smaller root systems.

Stand Alone Pool or Part of a System.

This may seem an odd heading but stick with me here.

This website is about self-sufficiency and hopefully helping get people from a consumer-driven process to a more resilient lifestyle.

With putting Fish in a pool, it doesn’t matter what location you are in, be it urban or rural; the simple matter is that Fish poop in the water, and it needs to be cleaned out by some method.

It can be a natural method like a natural swimming pool, or it can be mechanical like the drum filter we had on our pool system ( article link here), or it can be by plants in an aquaponics grow bed system. These plants can include ginger. “Can an aquaponics system grow ginger root?” details what to look out for.

It makes no difference how you extract it from the water. What matters is understanding fish poop is fertilizer. It is a resource that is available to you to use, so think about it for a minute.

This concept opens up the discussion to system design and putting appropriate technology to work in your favor. This is how you can build resilience into your life and make it fun and educational.

Picture a swimming pool full of Fish with a mechanical filtration system that feeds the fish waste directly into a bio-digestor; this digestor could supply methane gas to a cooktop, and the water overflow from the digestor could irrigate fruit trees.

Some of the fruit could go back to feeding the Fish. It is called a closed loop system, which aims to keep the nutrients on your property for as long as possible.

But that is for another post. It is a huge subject we are passionate about because it builds resilience and helps with self-sufficiency.

Conclusions

It is possible to keep Fish in a swimming pool, and there are many factors to consider. Do your homework before committing, and you won’t regret it.

We hope you found something here to help you decide what to do. It can be a big decision, and having as much info about the idea before you start should help. Enjoy the rest of the site.

Article by Tim Blanch for TheTropicalHomestead.com. He is a qualified Permaculture designer.