Can Tank Fish Survive in a Pond or Stream?

Releasing your tank fish to the wild can shock fish, leave them open to diseases and predators, and cause an issue for native wildlife.

Apr 30, 2023By Sara Payne
can tank fish survive in a pond or stream

Have your fish outgrown their tank? Do they seem cramped and unhappy? Are you just unable to care for them any longer? If you are considering releasing your aquarium fish into the wild, reconsider, as there are consequences to this action. Read on to find out why.

4 Reasons Releasing Fish into a Stream is NOT a Good Idea

goldfish swimming

1. They are Tropical Fish

Releasing tank fish into the wild is not a good idea. Many of the freshwater fish bought in pet stores are tropical fish. If you do not live in an equatorial region, your environment is probably not correct for your tropical fish.

According to PETA, store-bought tropical fish require more sunlight, warmer water temperatures (from 75-84 degrees Fahrenheit, year-round), and different pH balances than many local streams.

Without these temperatures carefully controlled, your fish is in danger of dying.

2. The Temperature Shock Could Kill Them

In addition to local streams having the wrong environment, tank fish are usually born and raised in a carefully curated tank environment. If you take them out of this perfectly adjusted environment, they may die of shock, according to scientists M.R. Donaldson, S.J. Cooke, D.A. Patterson, and J.S. Macdonald. Fish can die from as little as a .02 change in pH or a 2-degree difference in water temperature.

fish frozen pond

3. They Can Get Eaten by Predators or Develop Diseases

The United States Geological Survey (USGS) advises against releasing aquarium fish into local streams because the fish can suffer from parasites and diseases. Predators can also eat them once they are in the wild.

These tank fish have no experience living, hiding, and finding food in the wild. They will be very vulnerable once they are released.

4. They can Disrupt the Natural Ecosystem in your Area

Unless the fish in your tank exist naturally in your home ecosystem, they are probably not native to your area. Introducing non-native species to a new environment can be detrimental to an ecosystem.

If your fish live once released, they can upset the balance in your local stream. If there are no natural predators in the environment, these fish could become an invasive species. Invasive species can often out-compete the local animals for resources. They can destroy habitats and reproduce out of control.

In many places, it is illegal for people to release exotic fish into the wild. Unfortunately, many well-intentioned fish owners think this is the best way to get rid of fish they can no longer care for. However, there are other options.

What Should I do if I can no Longer Keep my Fish?

betta in tank

Instead of releasing unwanted fish to a local stream, return them to a local pet shop, find another fish owner to take care of them, or donate them to a school or other public place that houses fish. It would be better for your fish if they had another owner who would care for them and curate an aquarium for their specific needs.

If none of these options work, a veterinarian can humanely euthanize the fish by placing it in a container of water and placing it in a freezer.

Can you Place your Tank Fish into a Curated Outdoor Pond?

pond lilies

Many fish enthusiasts keep ponds in their yards. However, your typical tropical fish cannot survive in this environment because of their temperature requirements. Cold-water fish like goldfish, koi, minnows, Plecostomus, guppies, and paradise fare better in these ponds.

Even outdoors, your fish will need plenty of care, including flowing water, plenty of plants, a waste filter, a sufficient water level, and daily feedings. They will also need a safe location away from local wildlife that might feed on the fish.

During wintertime, when temperatures begin to drop, many types of fish will need to be brought indoors. Fish do not tolerate freezing ponds well. You can also buy heating systems to keep your fish pond at a constant temperature to help your fish survive the winter.

Although your intentions may be good-hearted, you should not release aquarium fish into a local stream or pond. Tank fish will have difficulty surviving in a pond or stream environment different from theirs. They may even cause damage to the local environment. There are other ways to get rid of unwanted fish, so check out local fish owners, pet shops, vets, and public institutions to see if they want your fish before choosing more drastic measures.

If you want to move your fish to an outdoor pond, thoroughly research how to maintain this environment to ensure your fish live their best lives.

Sara Payne
By Sara Payne

Sara is a mother of two and a high school English teacher who rediscovered her love of writing during the pandemic. She has 5 rescue cats: Neville and Luna, who are white cats with black and grey spots, and Ginny, Blue, and Fairy, who are calicos. Besides taking care of humans and fur babies, Sara enjoys gardening, crafting, and spending time in nature.