What Do Ocean Fish Eat

What Do Ocean Fish Eat?

There are billions, if not trillions, of fish in the oceans, and like humans, each individual species has its own particular diet that they follow in order to get all the nutrients they need on a daily basis. However, a common question is, what do ocean fish eat?

The diet of an ocean fish depends on the particular species of fish. Ocean fish are generally broken down into two categories: those who eat other fish and those who eat plants. However, there is a large portion of fish that eat both plants and other fish. 

This article will discuss what ocean fish eat. So keep reading! We have everything you need to know about the diet of ocean fish.

What Do Ocean Fish Eat?

The ocean is a vast place made up of numerous fish species that all have to eat on a daily basis in order to survive. Depending on the specific species, the diet will vary from one and another. 

The fish that make up the ocean population are often divided into three categories, meat or fish eaters, herbivores, and those who eat both fish and plants. 

Most fish that live in the ocean are all predators, meaning that they all eat other fish. In the sea, it usually works in simplistic terms; the larger fish eat the smaller fish, which continues up the food chain. 

Other species of fish will get their daily caloric intake from eating as much plankton as possible, and others just eat anything they can find on the ocean floor, whether they be small worms, crustaceans, tiny organisms, algae, or detritus. 

One specific kind of fish known to eat anything, whether it be plants, other fish, or everything in between, is the bright Angelfish. These fish will even eat sponges, which are a specific kind of ocean organism. 

Do Ocean Fish Eat Vegetables?

If you have an aquarium of fish, you may have been told that the fish require a certain amount of vegetables and meat to maintain a healthy and balanced diet. Vegetables for saltwater fish can include algae, seaweed, and even lettuce if the opportunity arises. 

This is no different for fish living in the open oceans, as from time to time, they will graze on all kinds of algae that are growing around the ocean floor. They will also eat seaweed and any other organic material they can find while swimming across the ocean’s depths.  

It has been observed in some aquariums that ocean fish that are kept in the tanks will eat almost any kind of vegetable, including; broccoli, squash, peas, romaine lettuce, and even squashes. Thus, it’s safe to say even fish know the benefits of a well-balanced diet.

Can You Feed Ocean Fish?

If you’re out on your boat in open waters, or you’ve somehow found yourself out at sea, and an idea of whether or not you can feed the fish you see swimming around you pops into your head, in some cases, it’s okay, depending on what you have to feed them. 

If you were to throw the fish some bread, just as you would the birds in the park, this is a bad idea and should be avoided. Bread will quickly bloat the fish and begin to cause a feeling of discomfort as it tries to digest this popular carb. 

Instead of bread and other glutenous foods, if you have any vegetable scraps, this is a better option to throw into the water when you feel like feeding ocean fish while at sea. On top of this, you’ll be providing the fish with nutritious calories instead of the empty ones they would receive with chunks of bread. 

How Long Can Marine Fish Survive Without Food?

When it comes down to how long marine fish can survive without food, it all depends on the particular fish species and its size. In general, most ocean fish will be okay for a few days and may even last up to a week without eating. 

If you have a marine fish as a pet, you will want to ensure that the fish is fed every two to three days; however, in exceptional circumstances, it will survive if it has to be longer between meals. It’s best to find someone who may be able to look after the fish if you’re gone for an extended period of time.

The idea, whether in the open ocean or your aquarium, is that while the fish may be able to survive for an extended period of time without any food, after a few days to a week, you risk compromising the health of the fish. 

Depending on what the fish eats in its daily life, this can also impact how long it can go without food. If the fish grazes on algae or plankton from the ocean floor, then it will certainly not be able to last as long as some of the larger fish who are eating whole fish for their dinner. 

How Often Do Saltwater Fish Eat?

Certain species of saltwater fish eat a lot more frequently than other kinds. In general, larger saltwater fish, such as a grouper, will eat a relatively large fish at once and often irregularly. They may only eat one or two large fish daily and be completely satisfied. 

Other smaller fish may spend their whole day eating plankton and algae from the ocean floor, as it requires an extreme amount of this kind of food to get their caloric intake for the day. 

In general, the fish who consume meat will eat anywhere from two to three times per day but can survive on one. The smaller fish eating much smaller fish may eat five times a day, and the vegans of the fish world may spend their whole day grazing on whatever kind of vegetable they can find. 


So, as you now know from this article, most fish in the ocean will eat other fish. However, some prefer to nibble on algae and other vegetables. If you’re ever in the position in which you have the opportunity to feed a saltwater fish, opt for vegetables as opposed to any kind of bread or carb.