How to Take Care of Goldfish in a Pond

Taking care of goldfish in an outdoor pond is a simple task. The biggest problem people run into is when they over think the task at hand and over complicate matters. Especially when it comes to feeding and overfeeding. This is the number one cause of poor water quality that pond owners face.

Goldfish in a fishbowl or fish tank

First, let me begin by saying this article deals strictly with outdoor goldfish and koi. I no longer keep any indoor fish aquariums. It’s funny, I remember a time when fish aquariums were really popular in the 1980s and 90s. Since then, the industry has steadily declined. It’s too bad, keeping a fish aquarium is a really fun and rewarding hobby. Still, it has nothing to do with the subject at hand so I’ll get started on outdoor ponds.

How to Take Care of Goldfish in a Pond

Feeding goldfish and koi

This is where most people run into problems. Did you know that goldfish and Koi eat plant life, certain forms of algae, and even insects? In other words, if you live in a rural or semi-rural area, there are a lot of bugs that the fish feed on. This means to feed them minimally. You also have to keep in mind that fish don’t require as much food as humans think. Feed your fish food in the form of pellets modestly. Throw some pellets in and see how quickly they get gobbled up.

Here’s another good sign that you’re overfeeding your goldfish. If after five minutes the pellets are still floating around the pond uneaten, you know that they’ve had too much. The excess food will eventually dissolve reeking havoc on the water quality which is the last thing you want. Your goal is to raise happy, healthy, vibrant fish whether they’re koi or goldfish. By the way, both fish are from the same family, namely the carp family. Overfeeding fish commercially processed foods primarily made from grains results in obesity and eventually disease.

Keeping the right amount of goldfish and koi in your pond

Another common issue I come across all the time is when koi and goldfish are left in overcrowded conditions. This also leads to a higher risk of disease in fish, particularly bacterial infections and skin lesions. Of course, there are special medications added to the water which usually solve such problems. Do you really want it to get to that point?

Keep the right number of fish in your pond according to its size. Besides that, fish don’t like being overcrowded and it stresses them out. Even so, of all the koi and goldfish ponds I’ve seen over the past ten years, at least 90% of them are overcrowded (and overfed), with poor water quality. It all comes down to common sense. Don’t put too many fish in your pond and don’t overfeed them. Cloudy pond water is a good sign that something is wrong. Heed its warning before a fish kill or algae bloom occurs.

Keeping pond water clean

This is your number one priority over everything else. Keep the pond water as crystal clear as possible. Clean pond water indicates healthy fish, plants, and other pond inhabitants. I’ve already talked about two ways of keeping your pond’s water clean, specifically by not overfeeding fish or overcrowding them. That’s a basic concept we should all agree with. Even so, sometimes situations arise that affect the pond’s water quality that isn’t the fault of the pond owner. For example, a bird such as a duck may transport duckweed or blue/green algae spores into your pond. While this is a major bummer, it comes with being a pond owner. Deal with it accordingly.

Catch problems early. Clean out excess algae and duckweed on a daily basis until you’ve conquered the situation. I know it can be done because I’ve had to do it myself. You must stay vigilant and certain products on the market can help the process along. While I said earlier that taking care of goldfish was generally easy, I never said taking care of the pond itself was. I await what challenges I’ll face this spring with my six ponds. While I’m not expecting anything, in particular, to go wrong, I’m prepared for just about anything that may happen. As long as I don’t have to dig up pond liner, I’ll be happy, and that’s very unlikely to happen.

Pond pumps and filters

While all six of my ponds run by their own ecosystems, in some situations pumps and filters are necessary. I’m hoping that’ll never be the case with any of my ponds but time will tell. Ponds that are overstocked and have excess waste such as uneaten food benefit from a pump and filter. While water changes may work well in indoor fish aquariums, outdoor ponds are a little different. Draining and re-adding water will mess up the sensitive balance of your beneficial bacteria leading it to start the process all over again. This means another bacteria bloom.

Bacteria blooms last anywhere between a week to a month, sometimes a little longer. Don’t confuse a bacteria bloom with an algae bloom. These are actually beneficial. You don’t want to treat your pond water with any chemicals during a bloom. Simply allow nature to take its course. Once the bloom clears up, and ammonia and nitrogen levels are where they’re supposed to be, you’ll have clear water again.

Important high quality submerged oxygenating plants

One great way to keep your pond clean is by adding high-quality oxygenating plants which stay submerged. These include such plants as hornwort and anacharis. While fish like goldfish and koi don’t need the high oxygen levels as largemouth bass, bluegill, or trout, these plants also do a great job acting as a natural filter for your pond. They literally feed off the fish waste and breath in the carbon dioxide fish emit from their gills. A perfect match. Other plants such as flowering water lilies also have a place in a pond’s ecosystem. Besides their aesthetic beauty, they produce oxygen in the water and absorb fish and other pond inhabitant waste.

Snails are good for a pond

Finally, I’ll mention just how important fully aquatic pond snails are to a well-balanced pond ecosystem. They also do their part in keeping your pond crystal clear. The only thing to keep in mind with snails is that in certain situations, they may mass-produce seemingly overtaking the pond. This is why you should go with non-invasive snails. Instead, try to get some snails from ponds found locally in your area. Even in the case of a snail infestation, they’re easily removed manually with a net, and some fish eat snails keeping their population in check.

All my ponds have colonies of snails of different species. I’ve never had a problem with an overabundance of snails. I once added invasive apple snails to my largest pond which I call the bass pond. This is a pretty large body of water and manually removing them was not really a viable option. I became extremely concerned as they were eating my beneficial oxygenating plants but luckily mother nature solved this problem for me. At night the raccoons and other nocturnal scavenging animals came out and walked the perimeter of the pond, picking large apple snails off that tend to stay at the water’s edge. After the raccoons discovered this new food source, I no longer had an apple snail infestation. I got lucky on that one.


Take care of goldfish and koi by not overfeeding them. Feed them only as much as they can eat after five minutes. Remove any excess, uneaten food. Also, don’t overstock your pond with too many fish. It’s extremely counterproductive in every way. Treat tap water by removing harmful chemicals with an inline filter or with a de-chlorinating product. Do this after adding new water to your pond every time. 

How to Take Care of Goldfish in a Pond