Goldfish and Koi fish are the most common species of ornamental fish in aquarium stores, and almost every store has them, which is by default the two ornamental fish species that a novice fishkeeper must come across. However, I have always found that one problem that people overlook is that they think goldfish and koi can be mixed together. This is a big mistake, and I need to talk to you about it today.
If you have kept goldfish and koi carp separately for a while, you will find that goldfish is a relatively quiet fish, while koi carp is a relatively active fish. The habits of the two fish are different. I will compare the similarities and differences between goldfish and koi carp in the following section, I believe that after reading this section and the final summary, you will know why goldfish and koi carp are not suitable for mixing.
Similarities between goldfish and koi fish
1. Wide-temperature fish
Both have a wide range of temperature adaptations, which is why we often refer to wide-temperature ornamental fish, also commonly referred to as goldfish and koi fish. Of course, there are other fish in nature that have a wide range of temperature tolerance, but the most common are goldfish and koi carp. The range of temperature adaptation here is from 0 to 30 degrees Celsius. Both are broad-temperature fish, which does provide the possibility for them to mix, but this alone is not enough for them to be able to mix together.
2. Both are omnivorous fishes
Both goldfish and koi fish have a very mixed diet of meat and vegetables, so those of you who have kept them will notice that water plants often give goldfish or koi fish a chance to chew them up for no reason. The way they eat, you can’t even tell they are eating water plants, they just dislike it a little bit, making it hard to notice. Also, some small fish will get swallowed from their mouths if they can get swallowed from their mouths. Of course they’re either hunting for food, or simply think it’s food.
3. Same ancestor
In fact, both goldfish and koi carp originated from China, according to historical records, the earliest time was in the Tang Dynasty, at first people kept carp in temples for releasing, then they found a red carp, which looked good, so they consciously did not release it. The red crucian carp was gradually indifferent, but at that time, Japan admired the culture of the Tang Dynasty in China, so they brought it back and bred koi carp. Hundreds of thousands of years ago, they came from the same lineage, but due to artificial breeding and selection, they have been artificially cultivated to be two completely different species.
The Differences Between Goldfish and Koi Fish
Koi fish are very active, because of their size and habits, they need a large range of water, for example, a 10cm Koi fish, you need at least a 60cm tank to have enough space for them, and a 20cm Koi fish, without a 2m tank, is far from enough for them to move around. That’s why it’s important that I’ve been suggesting that koi fish need to be kept in a pond when fishermen have come over and asked before.
Goldfish are different, they’re not as active, so they’re fat and round, and we see goldfish have a silly look to them. They are fine as long as they can have room 2-3 times larger than their body size to ensure that the water has enough oxygen in it. This leads to the fact that if you keep both goldfish and koi fish in a tank that is too small, the koi fish will often bruise the goldfish. At the same time, koi carp will also chase goldfish, banging against their stomachs, which can easily hurt them. This is due to the different habits of the two.
To sum up, although goldfish and koi fish have quite a few similarities, the differences in size and habits are enough to keep them separate and unsuitable to be kept together. And if you force them together, for goldfish, koi carp that are so active will keep bumping against them which is uncomfortable; for koi carp, the space is too small for them to stretch out, and they are prone to various problems on their bodies such as bloody fins. Overall not good for either, so either keep goldfish or prepare a larger area to keep koi fish.