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The Goldfish Gazette, Issue #117 Compatibility with other species
September 29, 2023

Goldfish Care Tips

A Free Monthly Resource For Goldfish Enthusiasts
September 2023
Issue #117

In This Issue
Compatibility with other species

Goldfish are often kept with other species of fish, but not all are suitable tank mates. Some present a danger to Goldfish, while others are in danger of being eaten.

Compatibility With Other Species

Goldfish are generally non-aggressive towards other species of fish, and this is often mis-interpreted by Goldfish Keepers that other species can be kept with them.

Some key areas where compatibility issues arise are as follows:

Water Temperature

Goldfish can live in a wide water temperature range, thriving in water temperatures between 15-23 degrees Celsius (60-74 degrees Fahrenheit).

This is the first compatibility issue to consider when introducing a new fish species. Tropical fish prefer warmer water temperatures in the higher range of 23 degrees Celsius plus.

This temperature would need to be maintained year-round; good for tropicals, but lifespan shortening for Goldfish.

Size and Eating Habits of Goldfish

Goldfish are opportunistic eaters and will consume any living creature small enough to fit into their mouths. This means that smaller fish species such as neon tetras, white cloud mountain minnows or guppies, would be at risk if housed with Goldfish.

Koi carp present the opposite problem. In a pond situation they tend to dwarf even the largest Goldfish which will only attain a third the size of a fully grown Koi. Koi have the same eating habits of Goldfish, but their size enables them to dominate the food at feeding time.

Avoiding Aggressive Fish Species

Larger, aggressive fish species can pose a threat to Goldfish. For example, cichlids are known for their territorial behavior and can harm or even kill Goldfish. Tiger Barbs, Black Widow Tetras, Betta Fish are all known to nip at the fins of other fish, especially ones with long flowing tails.

Are Plecos Dangerous to Goldfish?

Plecos, (Plecostomus), a type of catfish, are generally peaceful and can coexist with Goldfish. However, some of these fish grow quite large and some will suck on the goldfish's slime coat, causing stress and potential life-threatening injuries. Therefore, while plecos are not inherently dangerous to Goldfish, caution should be exercised when considering them as potential tank mates.

A more suitable catfish is the Bristle Nose catfish, (sometimes incorrectly called a Plecostomus), which grows much smaller than most Plecos. Having said that, some will start the same habit as they get older of sucking the slime off Goldfish for the protein, usually at night when the Goldfish are asleep.

If your Goldfish start trying to avoid your Plecos or Bristle nose, suspect they are attacking your Goldfish.

Do Goldfish Eat Snails?

Goldfish are known to eat aquatic snails. Some aquarists use Goldfish to clean out a pond or aquarium infestation of snails.

If you're considering adding snails to your goldfish pond or aquarium, opt for larger species, such as mystery snails or apple snails. These larger snails are less likely to be eaten by the Goldfish, making them a safer choice.

Compatible Fish Species

Some fish species are generally compatible with Goldfish. These include weather loaches, and rosy barbs. These fish species can tolerate similar water conditions and have comparable size and temperament to Goldfish, making them suitable tank mates.

By suitable I mean suitable for single tailed Goldfish varieties. Slower twin tailed varieties are not going to be able to compete for food unless some special feeding regime is employed such as using tank dividers during feeding.

Individual Fish Behavior

Despite general compatibility rules, it's important to remember that every fish has its own personality, and individual behavior can vary. Even if a fish species is generally considered compatible with Goldfish, close monitoring is necessary when introducing new fish to ensure that they are getting along.


Goldfish compatibility with other fish species is a complex issue that requires careful consideration of various factors including water temperature preference, size, eating habits, Goldfish variety and temperament of the potential tank mates.

As a general rule, single tailed varieties are the most suitable to be in a mixed species aquarium or pond.

Comments? Ideas? Feedback? I'd love to hear from you. Just reply to this e-zine and tell me what you think, or what topics you want to be covered.

Next Month's Topic

Goldfish Egg Incubation

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