Can Saltwater Fish Eat Freshwater Food?

Have you ever run out of food for your saltwater fish and realize that all you have available at the time is freshwater fish food?

This is a common concern and many people are not sure whether or not you can feed your saltwater fish freshwater food.

It’s important to only feed your fish the proper foods needed for them to grow and stay healthy.

In this article, I will explain the difference between saltwater and freshwater fish food so you can make the right decision for your fish.


Can you feed your saltwater fish freshwater food?

Yes and no. 

Marine flake foods contain a different mix of nutrients than freshwater fish foods. You should not supplement one for the other. This is important especially if you are looking to feed your saltwater fish and freshwater food over a long period of time. 

If you are in a pinch and need to feed them in the short term, then you shouldn’t have any concerns as your saltwater fish will eat the freshwater tropical fish food temporarily.  


Freshwater vs marine flake food – What’s the difference?

When deciding on the best fish food for your fish, it’s important to know their dietary requirements as not all fish are the same.

Marine flake foods are made with all marine fish dietary needs taken into consideration. It will contain all of the nutrition they need to be healthy. Freshwater flake foods are made with the dietary needs of freshwater fish in mind. All flake foods regardless if its marine or freshwater are made with ingredients based on the fish’s natural diet.

For example, let’s look at a high-quality flake food to see the difference in ingredients.

Omega 1 Marine flake food

Raw protein 43%

Raw fat 11%

Raw fiber 2%

Moisture 8.5%

Raw ash 10%


Whole Herring, Whole Salmon, Halibut, Black Cod, Seafood Mix (Including Krill, Rockfish, Shrimp, Squid, Clams, Salmon Eggs, and Octopus), Wheat Flour, Wheat Gluten, Fresh Kelp, Garlic, Lecithin, Astaxanthin, L-Ascorbyl-2-Phosphate (Source of Vitamin C), Natural and Artificial Colors, Vitamin A Acetate, Vitamin D3 Supplement, Vitamin E Supplement, Vitamin B12 Supplement, Riboflavin, Niacin, Pantothenic Acid, Folic Acid, Biotin, Inositol, Tocopherol (Preservative), Ethoxyquin (Preservative).

Omega 1 freshwater flake food

Raw protein 41%

Raw fat 12%

Raw fiber 2%

Moisture 8.5%

Raw ash 8%


Salmon, Whole Herring, Wheat Flour, Whole Shrimp, Wheat Gluten, Pea Protein, Herring Oil, Tumeric, Kelp, Garlic Powder, Spirulina, Mixed Tocopherols, Citric Acid, Asorbic Acid, Marigold Extract, Carmine, Annatto Extract, Vitamin E Supplement, Niacin, Inositol, Astaxanthin, Canthaxanthin, Riboflavin, Vitamin A Supplement, Vitamin B12 Supplement.

As you can see there are differences between the two foods.

The Omega One flake foods are available on Amazon here.


Marine Depot Aquarium Supplies

What do marine fish eat in the wild?


In the ocean, marine fish don’t have the option of being fed flake or pellet foods. They are in a world where they need to fend for themselves and eat what is natural for them.

Fish consumption includes things like microscopic bacteria, plankton, different types of algae, and other fish and invertebrates can all become snacks for marine fish.

Every fish in the ocean has its favorite food, but most will settle for anything they can get if they are starving.


How often should marine fish be fed?

On average, it is best to feed your saltwater fish 2-3 small meals per day.

This can be adjusted depending on the type of fish and whether or not they are juvenile or full-grown.

It is better to feed multiple small meals each day than one large meal.


How long can saltwater fish go without eating?

If you forget to feed your fish or are away for a few days, your fish should be fine.

Most fish species can generally last 3-4 days without feeding and up to a week is possible. 

Certain fish when added into a new tank may not eat for a few days. This is quite normal.


clown tang care

How can I feed my saltwater fish while on vacation?

If you are going on a vacation for more than a few days, you should arrange for someone responsible to feed your fish.

It’s important that they don’t overfeed them and even if they can only feed every second or third day, that is better than leaving it for a longer period of time.

You also have the option of using an automatic fish feeder which can be very convenient. This is the one I recommend. 

For me personally, I would prefer to have someone check on my tank and equipment while I am away and feed the fish while they are there.


Does frozen fish food need defrosting?

No, it is not necessary to defrost frozen fish food prior to feeding. Depending on the size of the frozen food and the fish you have in the tank, you can place the cube in the tank for the fish to eat.

I prefer to defrost frozen food in a small dish of tank water prior to feeding. It is much easier to control and not overfeed. Try to avoid having a block of food sitting at the bottom of the tank.

Most times it will get eaten but just keep in mind not to overfeed.

Also once the frozen food is defrosted, you should use it right away and do not re-freeze it. Frozen foods can be kept frozen for around 18 months.


Proper fish diet

best food for clownfish

Depending on the types of fish you are keeping, they may have varied diets. Fish species can either be herbivores, carnivores, or omnivores.

Their diet needs to consist of the proper foods they require.

Certain fish like the Yellow Tang is a herbivore and needs to have a plant-based diet. They love to eat algae and marine algae sheets. They will eat any pellet or flake food that is made for herbivores.

Carnivores are fish that need to have a meaty diet. They will most likely never eat algae. They can be fed shrimp, worms, copepods like the Green mandarin which will most likely only eat copepods. Some carnivores may even eat crustaceans and invertebrates.

Omnivores are fish that can eat both a plant and a meaty diet. Clownfish are a good example. They should be fed a variety of flake, pellet, frozen, and live foods.



Best flake and pellet food for saltwater fish

With so many options on the market today, it’s important that you choose a good quality food for your fish. Flake and pellet foods are the most common types of food to feed saltwater fish.

Some of the best options to choose from are:

Omega One

New Life Spectrum (NLS)

PE Mysis/PE pellet

These foods are available at Marine Depot. You can check today’s prices by clicking the link.


NLS flake food for clownfish


Another great food that all my fish love is Easy Masstick. It is a very unique food that can be stuck anywhere in the tank and the fish go crazy over it.

If you have any tangs in your tank it is great to have as they can graze on this food as they would naturally in the wild.

easy masstick fish food


When feeding your saltwater fish know that they can be different with respect to their dietary requirements. You want to feed them the proper foods for saltwater fish and only feed them freshwater fish food as a last resort or in a pinch. With certain fish species, you can get away with it in the short term but they should never be fed foods other than what is recommended for them.


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