Every time I see a pond, or visit someone who owns a pond, I wonder if my fish would be better off living in a pond compared to their regular aquarium. But I was not sure whether they would actually survive, so I jumped online and asked around.
Can aquarium live fish in a pond outside? Yes, you can keep aquarium fish in a pond as long as you provide them with the right environment and water parameters. This differs per fish species, but most aquarium fish are tropical fish which require warmer temperatures.
So you can keep aquarium fish in a pond, but just like an aquarium you should know the ins and outs before you commit. In the rest of the article I will teach you everything I know. +
Matching the desired water parameters
Most fish that we keep in our freshwater aquarium are tropical fish. This means that they are found in tropical regions in the wild, and require tropical water parameters to live. Tropical temperatures basically. This is also why we add a heater in our tank to control the water temperature for us.
However chances are that the temperature drops too low in the autumn and winter. This means that you can keep aquarium fish outside during summer, but you should move them inside as soon as it gets too cold for them.
But what are these correct tropical temperatures? Well, you should make sure the temperature stays above 65 °F (18 °C) at night and above 72 °F (22 °C) during the day. Anything below that is too cold for tropical aquarium fish, which weakens their immune system and makes them prone to diseases.
Next to the correct temperature, your pond should be ready for fish and match a couple of criteria before fish are able to thrive in it.
To make sure the temperature is more or less stable and does not fluctuate wildly in the pond, the pond should be (partially) buried underground. This makes sure that the water heats up and cools down gradually.
It is very important that your pond has some deeper areas. This makes sure that the overall temperature of the pond does not skyrocket when there is a lot of sunshine. When your entire pond is shallow, which means there is little water to heat up, temperatures can rise well above 86 °F / 30 °C. This is lethal to your fish.
There should be proper filtration and water circulation in your pond. While a lot of ponds can do well with just a lot of live plants to filter the water, you need to make sure the water is properly aerated and moving. You can do this my adding something like a fountain, waterfall, filter, skimmer, air pump or circulation pump to your pond.
This is a good and cheap way to circulate the water in your pond. The link will take you to Amazon.
Add enough live plants / rocks and wood to provide your fish with sufficient hiding places. This is important because your fish will need these to feel safe.
What fish can you add to your pond?
There are a couple of things you should take into account when thinking of what fish you are going to keep in your pond. If you can only keep fish in an outside pond for a part of the year, you will need to be able to take them out of the water again in the autumn.
This means that really small fish like livebearers (guppies, mollies, platies, swordtails) are going to be more difficult to catch compared to bigger fish.
Also, what I want to add here quickly as a side note, is that goldfish are pond fish instead of aquarium fish. While a lot of people keep them in their aquarium, these fish will grow quite big and need the space that a pond can provide for them. And they are not tropical fish so do well in ponds that stay cooler. They can even survive winter when the pool freezes over.
If you are able to keep fish outside year round, I would definitely add small fish like the livebearers I mentioned above. They are going to breed like crazy and will keep your garden relatively free from mosquitoes as they will eat their larvae.
Acclimating the fish
When adding aquarium fish to your pond, you definitely need to acclimate them. The least you should do is temperature acclimate them in the same way you temperature acclimate your aquarium fish when adding them to your aquarium.
Put the aquarium fish in a plastic bag with a good amount of aquarium water and let them float in the pond. This way the water they are in will slowly turn the same temperature as the pond.
But chances are that the water parameters like for example the pH and the hardness from the pond are different compared to your aquarium. To let your fish slowly acclimate to these new conditions, you should fill a bucket with aquarium water and add an air stone. Put your fish in there and slowly add some pond water to the bucket. Just use a cup for this. Keep adding pond water until the ratio is about 50/50 over a period of an hour or so.
This will make sure that your fish are ready for the pond’s water and the water parameters.
What to feed the fish?
When you are keeping fish in a pond, they will be able to find a lot of food on their own. Think of algae, biofilm and all sorts of mosquito larvae and other insects. This will be a major part of their diet in a pond.
However, you can not rely that this is going to be enough. Especially if you are keeping a bunch of fish in a pond. And especially especially if you are keeping livebearers or other fish that breed, as their population size will drastically increase over time.
This means that you are going to supplement their diet using regular commercial food. You can add some once a day, and make sure you are not overfeeding them. That is probably one of the most important things, make sure they eat everything you throw in there. Everything that they do not eat will start rotting and polluting the water.
That is one of the risks of keeping fish in a pond, it is hard to keep track of how much they are eating. But what other risks are there?
Risk of keeping fish in ponds
So the first one is rotting food. This will seriously mess with your water conditions and will force you to do more water chances.
Another source of rotting stuff is going to be leaves. Especially if your pond is under some trees, you will have a lot of leaves in your pond in autumn. To prevent this, it is best if you get a net to cover your pond with to catch as much of the leaves as possible.
There are also a lot of predators that might want to snatch your fish. Especially bigger fish like goldfish and koi. This could be your local heron but also other birds. If you are keeping livebearers in your pond chances are that their population will grow faster than any predator can eat them.