A mind boggling question explored!
One of the most asked questions when it comes to goldfish is “Do Goldfish Have Stomachs?” Let’s take a dive into the digestive system of a goldfish and find out what they are really made of! There have been many theories about whether or not a goldfish has a “stomach” or if they digest their food another way. The answer can be easily found by simply examining the inner workings of a goldish’s digestive system. So without further a due let us take a look at these interesting facts.
Goldfish Mouth:
A goldfish will begin by swimming to the surface of his aquarium (or pond) to consume his fish flakes, pellets, or insects that have been provided to him. The goldfish does have “teeth” that are called pharyngeal teeth because they are located in his pharynx. Once the goldfish opens his mouth to consume his food he creates a suction that pulls the food into his mouth. Any tank water that has been sucked in with his food will then be dispersed through his gills and back into the tank.
Goldfish Pharynx:
The food he has sucked into his mouth will then move into his pharynx. This next step is located at the back of the goldfish’s mouth and is the location of his taste buds and pharyngeal teeth (previously mentioned). The goldfish will use these teeth when he consumes heartier meals such as insects, plants, roots, worms, and veggies. A goldfish usually won’t need his teeth if he is only being fed fish flakes as these will dissolve. His teeth will make the food much smaller and easier for the next step to take place.
It is important to point out that a goldfish’s “teeth” are not the same as human teeth. A goldfish has two teeth on each side of his pharynx (typically four teeth in total). They will also have much smaller teeth waiting at the base of each tooth until those teeth fall out, and then the baby teeth will move in.
Goldfish Esophagus:
A goldfish’s esophagus is much shorter than ours. In fact, they have one of the shortest esophagi of any species. Once the food has been “chewed” and made into smaller bits, it will then move into his esophagus in preparation for the next stop along the digestive tract.
Goldfish Intestines:
A goldfish’s digestive system is equipped with two sets of intestines.
Goldfish Intestinal Bulb:
The intestinal bulb is also commonly referred to as the “midgut”. This section of the intestines plays a major role in a goldfish’s digestive system. His body uses the midgut to store the recently consumed food but only temporarily. During this “storage period,” the goldfish’s body is absorbing certain nutrients the food has to offer including lipids. In fact, the midgut (or Intestinal Bulb) can swell to make room for the amount of food consumed. Depending on how much food needs to be stored at one particular time, the midgut can swell to be about three times its original size. After the “storage period” is over the food will move on to the final step in the goldfish’s digestive system.
Goldfish Caudal Intestine:
Finally, the food 
A goldfish’s entire digestive tract is uniquely about two times longer than the body is. That being said, it is also an extremely fast digestive system. Proper feeding of a goldfish is more important than you may have realized before reading this article. Although goldfish love various types of food (insects, algae, worms, veggies, and fish food), they do in fact lack a stomach.
What does this mean?
It means that they cannot store food for an extended period of time or digest large quantities of food at a time. Therefore, it is essential that you choose a well-rounded diet for him, feed him small (digestible) meals multiple times per day. Goldfish are natural foragers and muncher. They will be healthier and happier eating smaller more frequent meals.
A lack of stomach also means that a goldfish can fully digest their food much more quickly than someone with a stomach would digest his or her food. This is usually what is meant by the statement “goldfish are messy fish”. Goldfish can digest their food much quicker than a creature with a stomach can, which also means that they are expelling their digested food much more frequently than someone with a stomach would. Hence, why goldfish specialists will recommend frequent water changes and tank cleanings. Sure, there are good bacteria that live in an aquarium and cleaning an aquarium too often could harm the natural ecosystem. However, allowing your goldfish’s natural waste and other less good bacteria to accumulate would create unsanitary living conditions for him which can also lead to illnesses (and eventually death).
Another important note to take into consideration when deciding on goldfish as pets is that they do require a filter. Many first-time goldfish owners will purchase a fish bowl or a small tank believing that it is all they are going to need. Unfortunately, they could not be more wrong. First of all, goldfish can grow to be quite large. Which means they require a large enough tank for them to grow into. Also, simply purchasing a fish bowl or small aquarium kit usually means that it does not include a proper filtration system.
The filtration system is essential for goldfish because of their lack of stomach (frequently expelling digested food into their tank water as previously mentioned). Your goldfish deserve to be given a beautiful place to call home. They require a good filtration system, décor to swim through, live plants to nibble on, and a variety of meal choices. However, most of all they need owners who will take them time to change out their tank water correctly and clean their aquariums.