While goldfish are not naturally aggressive fish, you still need to be very careful when choosing tank mates for them. There are four main reasons why most fish do not do well in a tank.
- Goldfish are considered cold water fish – in a goldfish aquarium there is no need for a heater. As long as the temperature in your home is between 65 and 75 degrees, they will work fine. This can be a problem for many other fish.
- Goldfish produce a lot of ammonia: The amount of ammonia they produce can pose a danger to other breeds of fish. However, if you follow a water change schedule that includes changing at least 75% of the water in the tank at a time, there are some breeds that can be tank mates.
- Fancy Goldfish Are Slow – If you place faster moving fish with fancy goldfish, they may eat the food before the goldfish have a chance to eat enough to stay healthy. This may even be true for other types of goldfish.
- Fancy goldfish can be preyed upon by more aggressive fish – many other breeds of fish have been known to attack the tails and fins of goldfish. When their fins are damaged, they can have difficulty swimming and get sick.
That said, there are some breeds of fish that you can put in tanks with goldfish. To do this, you will need to have a fairly large aquarium. Goldfish need a lot of space and most of the fish that can keep them company are training fish, so you’ll need to make room for at least three of them.
Some fish that are happy to share an aquarium with goldfish include:
- Pink Barbs – This non-aggressive subtropical fish is a nice addition to a goldfish aquarium. Their colors are similar but have a more pinkish hue. They grow 4 to 6 inches long at maturity, so your goldfish will most likely not eat them.
- Zebra Danios – This is a good choice only if you don’t have fancy goldfish. Danios are fast enough to avoid becoming a snack for common or kite goldfish. However, do not place them with fancy goldfish because they are also fast enough to prevent slower fish from getting enough food.
- Rubbernose Pleco or Bristlenose Pleco: Do not add a common Pleco to the tank. Common plecos are known to have a coating of slime that sheds from goldfish and causes illness. However, Rubbernose or Bristlenose varieties make good goldfish companions and will help control algae in your tank.
If you are still unsure about adding other fish breeds to your aquarium, you can find variety even among goldfish breeds. Just remember not to put the skinny and fast goldfish with the fancy goldfish. They are faster than the sleek breeds and will gobble up food before their slower relatives can eat.