Why are there Goldfish in my Water Trough?

The functions the goldfish perform (and don't perform) in our farm water troughs

I started keeping goldfish in my water trough about five years ago. I was researching about permaculture and animal husbandry practices and came across the concept of introducing goldfish into the barnyard. It sounded off-the-wall at the time, but after some research I headed to the pet store and bought a small bag of fish. I decided on four for my 100-gallon tank. About five or so years in now, I can honestly say that they definitely make a difference. Why do I keep them? Mosquitos.

Mosquitos are readily present here in central New Jersey, especially in our wooded and agricultural pocket. They eagerly populate in standing water—anything from standing puddles, to buckets, to still ponds and troughs… water that is not moving or flowing is fair game for egg laying. In just 24-48 hours mosquito eggs hatch into wiggly larvae. After only four days to a couple of weeks (species depending) mosquitos mature and are ready to put a damper on that summer evening magic I wait the rest of the year to experience.

Here at the farm we use several practices to reduce our mosquito numbers and it shows; a walk across the street to chat with the neighbors leaves us covered in bites in mere minutes. On our own property, however, attacks are minimal. This is thanks to keeping guinea fowl, maintaining a healthy bat and frog population, and planting loads of fragrant companion plants in my food forest guilds that mosquitos supposedly despise. But every little bit helps and so enter the goldfish.

I currently have the same four fish who started out as quite small 9-cent babies in my 100-gallon stock tank. I have another two goldfish in my 35-gallon sheep stock tank. The fish overwinter well in the troughs, especially because they have the added comfort of a submerged trough heater in the winter time which I use for the horses (the troughs are not in the barn). That said, they live in the stock tanks year-round. Here’s a few answers to other commonly asked questions I receive:

Do you feed the fish?
The fish require no supplemental feed; they eat the mosquito larvae on the top of the water, and also eat the bits of hay and forage that fall from the horses’ mouths when they drink.

What about aeration or a bubbler?
Because my draft horses are so large and require 35 gallons of water each per day—and I also have five sheep to one 35-gallon tank—I’m refilling water troughs constantly. The continuous refilling generates clean water full of bubbles, and the animals only add more as they play with their water before they drink. The fish get the aeration they need without a pump, the food they require, and a large tank for swimming all while keeping our mosquito population down.

Do the horses ever eat the fish?
No—they swim to the bottom when the horses approach.

Do any other animals or birds of prey hunt the fish?
Nope—not once here on our farm. We have a healthy population of fisher cats, raccoons, heron, bear, etc. and haven’t had an issue. We also keep livestock guardian dogs to keep wildlife traffic away which helps.

How do I know they’re healthy and thriving?
My vet friend says as long as they’re eating, creating manure, growing, and swimming they’re doing great. He says their color is super vibrant and he thinks they’re very healthy and happy.

Do they help with parasites?
I’ve heard this theory but haven’t really looked into it. I undergo other efforts for natural parasite prevention, and the fish are just for mosquitos.

Do they clean the trough and reduce algae?
No, they don’t. They are purely for mosquito control.

Do you use the fish manure?
Fish manure is loaded with nutrients. These troughs are drained for the greenhouse on a gravity fed system when we want to fertilize crops. I simply outfitted my troughs with a spigot on the bottom.

How do you clean the water trough?
I scrub my troughs once a week. To do so, I dip a 2-gallon bucket into my trough and make sure it’s half-full of water. Then I carefully tip over the stock tank, allowing water to drain out slowly. When there’s about an inch of water left in the tank, I grab the fish. I use my hands or a small net can work too. I place the fish into the reserved water previously scooped from their trough. Once all fish are deposited I move forward with scrubbing the trough as usual.

Lots of goldfish-rights activists out there believe this is a poor habitat. I firmly believe it’s much healthier than a glass bowl as they have daily water changes, loads of bubbles, no forgotten feedings, and 100 gallons to swim around in.

You can find my full video with everything you want to know from my YouTube channel below: