Do Goldfish Need a Filter?

Fin Rot in Goldfish


You’ve seen goldfish surviving in bowls without aeration, filtration, or air stones. Perhaps you once owned a goldfish that behaved in this manner. Some goldfish can live for decades in this kind of setting, which frequently sparks debates about the morality of keeping goldfish both in a bowl and in unfiltered environs. You might be wondering if goldfish actually require a filter after reading this. The information you need to know about goldfish and filters is provided here.

A Fiction

The notion that goldfish require a filter is untrue. As you may have observed, goldfish don’t truly require filtration and can live a long time without it. Tish, the goldfish with the longest lifespan, lived in a typical fishbowl for 42 years. Even if your goldfish doesn’t require a filter, there are still some important things you should know about goldfish and water filtration.

Without a filter or other aeration source, you might be wondering how goldfish can breathe. How do they add oxygen to the water? A labyrinth organ is a unique organ found only in goldfish. The labyrinth organ works similarly to the way the lung does. The reason goldfish can survive so long without water is because it permits them to breathe indoor air. This means that your goldfish can breathe even in low oxygen situations in an unfiltered environment by gulping air from the air around the bowl.

The Facts

Even while goldfish may not require filtration, providing them with high-quality filtration is a really, really good idea. Goldfish make a lot of waste since they are high bioload producers. Without filtration, these wastes accumulate in the water. This means that if you are keeping goldfish in a 2-gallon bowl without a filter, you should frequently replace the water. Probably once or twice a day! Waste items are accumulating in the water if you don’t execute frequent enough water changes, which can make your goldfish ill. Poor water quality is the main reason for sickness in goldfish.

Red Cap Oranda Goldfish

It is not acceptable to neglect routine water changes while keeping goldfish in an unfiltered tank or dish. To find out if your tank is holding ammonia and nitrites, which can be harmful to your goldfish, you should check your water parameters weekly or more frequently. This can assist you decide how regularly you should do water changes if you are checking your parameters several times a week.

Filtering Methods

There is a filtration option that will help maintain water quality regardless of the size or form of the tank or bowl your goldfish is residing in. The main goal of filtration is to create an environment that encourages the growth of good microorganisms. Since these bacteria need oxygen to survive, an environment without filtering or aeration will not support their colonization. The nitrogen cycle, which turns harmful ammonia and nitrite into nitrate, which is less harmful and easier to manage, depends on beneficial microorganism.

What size filter do goldfish require?

There are several sizes of exterior and interior filters. However, the actual size of the filter is not what matters. The term is “flow rate.”

The volume of water filtered each hour is known as flow rate.

Aim for a flow rate that is at least five times your tank’s volume per hour.


Even though it’s not required, giving your goldfish filtration is typically the friendliest course of action. In addition to enhancing the water’s quality and the atmosphere overall, some goldfish like playing in the currents and bubbles created by filters. Without a decent filtration system, keeping your water at a good quality might be challenging. Your goldfish may become ill or possibly pass away due to poor water quality. Even in a tiny habitat, there are many fantastic filtration methods available for goldfish. Proper filtration is an investment that will keep your goldfish healthy and content for many years.


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