One of the most common misconceptions in the aquarium world is that fish grow to the size of their tank. This myth is unfortunately still spread by some pet shops, but the truth is that it's absolutely not true!
The size of a fish is not determined solely by the size of the aquarium, but by important factors such as diet, water quality and rearing conditions.
For example, I've seen a 20-liter aquarium with a giant goldfish in it, and a 200-liter aquarium with a miniature goldfish. This shows that the size of the aquarium isn't the only factor; it depends on other factors.
How does a fish grow in an aquarium?
The size a fish ultimately reaches is primarily determined by the conditions in which it grows. Nutrition and water quality are crucial. The better the nutrition and water quality, the healthier the fish will grow. Poor conditions can seriously affect growth.
Fish with dwarf growth due to poor growth
Fish can also suffer from dwarfism! When they receive insufficient nutrition early in life or grow up in poor water conditions, this is reflected in their eventual size. Discus fish are particularly susceptible to this. Young individuals need to be fed well several times a day. If they don't, they will remain small, making recovery virtually impossible.
The fish's body then doesn't receive the necessary nutrients, making growth impossible. Some species, such as goldfish and fantails, can sometimes resume growth, even after a difficult start.
Can fish that are not fully grown harm you?
Yes, fish that don't reach their full potential are more susceptible to various problems. They can develop deformities, are more susceptible to disease, and are more likely to be eaten because smaller fish literally take up less space in the mouths of their larger counterparts.
A goldfish or fantail that suddenly grows significantly?
This is common, especially with these carp species! Goldfish are sometimes kept in aquariums that are too small, such as a 30-liter tank. While one goldfish remains small, another can grow enormously in the same tank. This often has nothing to do with the size of the aquarium itself.
It often comes down to water quality. If you connect such a smaller aquarium to a better filter and perform weekly water changes, both goldfish can grow as they should. What you often see is that once goldfish are moved to a larger aquarium, they experience a growth spurt. This is due to the cleaner conditions and increased filtration capacity.
Preventing dwarfism and deformed fish
It's therefore essential to provide good nutrition during your fish's growth phase to prevent stunted growth and deformities. This phase is crucial for their development.
It's also important to stick to your water changes and do them on time. We explain exactly how often this should be done for your aquarium in our article " How Often Should You Change Your Aquarium Water? "
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