There’s a dizzying array of fish foods out there, and sometimes, you might accidentally grab food formulated saltwater fish when you own freshwater fish.
Can freshwater fish eat saltwater fish food? Technically yes, but they shouldn’t because saltwater fish have different nutritional needs. If you run out of freshwater fish food, you can feed them live feed and certain human foods. Several alternative foods can fit your fish’s needs.
If you do end up without fish food, you can easily assess what your fish requires and feed them surprisingly common foods.
What Are the Differences Between Freshwater and Saltwater Fish?
Part of what makes people wonder whether freshwater fish can eat saltwater or marine fish food is the similarities between the two kinds of fish. While fish are certainly diverse in colors, size, and appearance, there aren’t any significant anatomical differences between marine or freshwater fish.
One difference is obvious – saltwater fish live in saltwater environments, while freshwater fish live in freshwater ecosystems. Marine fish process the salt in water differently than freshwater fish do.
Freshwater environments are typically much more varied in water salinity, available food, and temperature, which makes freshwater fish much hardier. Saltwater fish environments don’t change as much, which makes them less adaptable.
Because their environments are different, their natural diets are different. For instance, you won’t find a coral reef in a lake, so feeding a fish that lives in a lake something that’s exclusively found near coral reefs probably won’t be the best choice. That’s one reason why you can’t feed your freshwater fish saltwater fish food.
What Do Fish Typically Eat?
Fish food for both saltwater and freshwater fish typically comes in three forms: dry, live, or frozen. Dry foods are flakes, pellets, or crisps, which you’re most likely to see in your pet store.
Live foods are living creatures that you feed your fish, like worms or larvae. Frozen foods are typically living foods that have been frozen for convenience. Most fish food on the market comes in flake form, for good reason. Most fish will eat it, and most are formulated for optimal nutrition.
Pellets are larger, more resistant to degradation, and heavier, which is good for bottom-dwellers. Crisps are in between and are an excellent choice for fish throughout your tank.
Live foods are great for carnivorous fish since they can hunt for their prey as they would in the wild. Some commonly used live foods are:
- Blood worms
- Brine shrimp
Frozen fish food frequently combines both plant matter and proteins. It is a good choice if you want something shelf-stable that also has a lot of nutritional value.
Consequences of feeding them the wrong food
Just like humans don’t thrive on a diet of fast food, your fish won’t thrive if they have to eat food that doesn’t match up with their needs.
Fish require a specific balance of proteins, fats, vitamins, and minerals. Typically, that looks like:
- Fats: 8 – 10% for carnivores, 3 – 5% for herbivores
- Carbohydrates: 25%, though some can tolerate up to 40%
- Fiber: No more than 4% for carnivores, 5-10% for herbivores
- Protein: 45% for carnivores, 15 – 30% for herbivores. Young fish can need up to 50%.
The nutritional needs for omnivorous fish – or fish that eat both meat and vegetables – fall in between.
Straying away from that balance could cause liver disease, digestive distress, bone diseases, scale problems, and even death.
However, the biggest problem that most owners face when feeding their fish is feeding them too much. Limit feedings to two to five minutes at a time, twice daily. A fish can still die young if they’re overfed healthy food.
I Ran Out of Fish Food. Now What?
Life happens – maybe your food delivery got delayed, or perhaps the food you usually give them is out of stock for a while. It’s okay! Freshwater fish are known for being sturdy and adaptable, so there are plenty of suitable, easily accessible alternatives for you to feed them.
Here’s what to consider when deciding on an alternative food for your freshwater fish:
What kind of fish are they?
The first thing to consider is possibly one of the easiest – what kind of fish do you have? Consider all of the fish in your tank since they will all probably have different needs.
For instance, say you have a gold barb and a betta fish. Gold barbs are omnivorous, peaceful schooling fish who live in the bottom or middle of the tank. Betta fish, on the other hand, are carnivores who generally can’t live with others of their own species. You’ll have a completely different approach for each.
There’s also the matter of your fish’s size. A tiny guppy might get nutritional benefits from jumbo brine shrimp, but they’re way too big to fit into a guppy’s mouth. The reverse is also true.
Imagine having to survive on spinach cut into teeny pieces for the rest of your life. It would definitely be frustrating to get your fill.
Make sure the size and type of food fits your fish’s physical capabilities.
What’s their diet in the wild?
As mentioned above, fish can be carnivores, omnivores, or herbivores. Luckily, omnivorous fish are pretty common, which means you have a wide range of things to feed them.
Here are some common freshwater fish and what their diets are:
- Carnivores: Jack Dempsey cichlids, bettas, and killifish
Omnivores: Barbs, goldfish, mollies, catfish
Herbivores: Chinese algae eaters, silver dollars, plecos
Knowing what your fish prefers will narrow down your search significantly.
Also, just because a fish is a carnivore doesn’t mean it can eat any kind of meat. The same applies to omnivorous fish – just because they can eat a variety of things doesn’t mean you can throw just anything into the tank. More on that later.
Where do they typically live in the tank?
You’ve probably noticed that some of your fish linger near the surface, while others stick close to the bottom of their tank. It is not a matter of your fish’s energy – they’re just mimicking how they live in the wild.
Fish typically live in three different sections of the tank: the bottom, the middle, and the surface. Fish can move in between the sections if necessary, but it is essential to choose foods that make it easier for your fish to feed.
An excellent way to determine what foods work for various kinds of fish is to look at the direction their mouth is pointed in. If it is pointed up, they will likely go for a food that floats. If pointed down, they will probably enjoy a food that sinks to the bottom. If their mouth points forward, they can do either.
Choose alternative foods that your fish can eat with ease. While many of the alternatives we will get into won’t float as nicely as flakes, knowing where your fish hangs out will help you place food in a place they can reach.
Will Your Fish Like the Food?
Even if your fish seem to eat everything in a matter of minutes, they will likely leave some bits behind, especially if they don’t like a new food. Fish can be finicky, just like us.
Those uneaten bits go on to affect the environment of your tank if left alone, sometimes drastically.
The biggest risk that decomposing food poses is its ability to change the delicate chemical balance in your tank. According to Aqueon.com, uneaten food left in your fish’s tank can do the following:
- Releases toxic ammonia and nitrates, which can stress out or kill your fish
- Uses up oxygen in the decomposition process, lowering the levels of dissolved oxygen in the water, leading to fish stress
- Drops the pH in the water by releasing carbon dioxide
- Clogs your filter, which can lead to mold, mildew and decreased water circulation
Pay close attention to how your fish eat their new food source. You might have to switch up your tank cleaning routine if they don’t take to it as well as their regular food. A good rule of thumb is to remove any larger chunks of food within an hour of your fish enjoying it, just to keep the environment stable.
This variable is hard to control since you don’t know what your fish will like until they try it. Introduce the food slowly and adjust if you see the food isn’t being eaten.
What’s Your Budget?
Part of the reason why flake fish food is so popular is its affordability. While you should always buy the highest quality fish food you can afford, the reality is that some kinds of foods will probably be out of our price range.
Some of the foods on the list below are commonly found in your kitchen, or even free if you look in the right place in your garden. Others might require visiting a specialty store, which will take some of your time too.
This is less of a worry when it comes to finding alternative food sources for your fish since many of the foods are affordable or free.
What Alternatives to Freshwater Fish Food Are There?
There are a lot of alternatives to the traditional flakes, pellets, or crisps you can buy at your local pet store or favorite online store. Many of them are right there in your kitchen! Here’s a breakdown of the alternatives you can feed your fish:
#1 – Frozen or Raw Meats
If your fish is a carnivore, all you need to do is check in your freezer or pick up something extra at the store. Carnivorous fish can eat small pieces of shrimp or non-oily fish like cod or tilapia if you run out of food for them.
Salmon is common in stores, but it shouldn’t be fed to freshwater fish. It’s a little too oily, which is hard for them to digest and causes more mess in their tanks.
Also, meat-eating fish should stick to aquatic creatures for their food – Carnivorous or omnivorous fish shouldn’t eat land animals like pork liver or beef heard, since the hormones that cows and pigs have will likely damage your fish’s organs and be hard to digest too.
#2 – Insects or Worms
This treat is great for omnivores and carnivores alike. Fish sometimes eat larvae or insects that had the misfortune of falling into the water. You could pluck larvae, like mosquito larvae, from your garden or standing water for them.
Or, if you’re not interested in digging around in the dirt for worms or other bugs, you can buy worms at a lure and tackle shop. You can also raise mosquito larvae for your fish, as shown in this video. Fair warning – the video has a lot of close-ups of insects (as you might expect from a video about mosquitos.)
Other good choices include the following, which you can buy online or in a specialty pet store:
#3 – Hard-Boiled Egg Yolks
Small fish like egg yolks, though they shouldn’t be a large part of their diet. Adding a sprinkle or two of grated yolk into your fish’s tank every once in a while won’t hurt. The yolks also make a mess in your tank, so it might be best to give them a food like this before cleaning up the tank, like this video shows.
#4 – Vegetables
Omnivores and herbivores love vegetables, especially if you pick the right ones. Leafy greens mimic seaweeds in their environments and pack in a lot of nutrition that can help them thrive. Other vegetables that don’t look anything like what they’d encounter in the wild can be great for them too.
Pick fresh over frozen, if possible, and cook them until they’re soft. As you would with any fish food, make sure the size fits your fish’s mouth. Cooking the food until soft can make it easy for fish to eat whatever you put in their tank.
Fish really like:
- Lima beans
- Seaweed (or nori strips, found in the Asian aisle at the grocery store – make sure there aren’t any soy additives.)
As always, make sure that you remove any parts of the food that the fish don’t end up eating.
#5 – Fruit
Fish even enjoy fruit! The natural sugars in fruit can increase algae levels in some tanks, so make sure you get any pieces your fish leave behind (if they do.)
Fruits that fish enjoy include:
Here’s a video that shows fish enjoying watermelon and bananas. Note that the owner cuts the fruit into very thin pieces and removes what’s left after his fish is done.
#6 – Algae
This is a great and easy option if you have a tank of herbivores or omnivores. Algae that grow on the items in your tanks can be eaten if necessary. Fish enjoy it, and it gives you more time to get them their usual food.
You can also feed your fish algae tablets like these (AMZ link) though if you’d like something inexpensive, sticking with the homegrown stuff is both good and time-efficient.
#7 – DIY foods
Yes, you can even make a special food blend for your fish, though this is probably best left for more experienced fish owners.
DIY fish foods are typically made of the fresh food ingredients listed above plus vitamins, bound together with gelatin or agar. Fish like garlic too, which has anti-bacterial properties and increases their appetite.
Here are a few easy recipes to check out– one recipe is seafood, vegetables, gelatin, and fish vitamins, which you probably have at your house already. If you don’t, you can get the ingredients at any grocery store.
Since all fish have specific needs, make sure you do your research first to make the food with a proper micronutrient balance. Here’s a video of someone making fish food. Note that he cuts up the pieces to fit the size of his fish, even though he could have left the food in big chunks.
You can even make it into flakes, as shown here, though it’s a time-intensive process that might not be worth it in the long run.
What Shouldn’t You Feed Your Fish?
Freshwater fish might be hardier than their saltwater counterparts, but that doesn’t mean they can eat anything. Aside from the exceptions to the categories above that have already been mentioned, several foods should never go anywhere near your fish’s tank.
Fish should rarely eat:
- Rice or pasta – these foods can cause lethargy, though they might like the taste
Fish should never eat:
- White bread – it can cause severe, sometimes life-threatening bloating
- Sugar (excluding fruit) – it’s bad for your tank and not great for humans either
- Anything extremely fatty – fish should eat a high protein, low-fat diet.
Freshwater fish are very adaptable, even when you run out of their preferred food. With a few simple staples from your kitchen, you can keep your fish full and happy.