What you need to know about frozen foods

Why are frozen fish foods beneficial?

Frozen foods give us access to cuisine options simply beyond culturing in captivity, such as krill and Calanus species. This allows us to offer our aquarium fish something that is close, if not identical, to their natural diets.

This means these foods can be extremely helpful in getting newly purchased fish to begin feeding. While some species, like some species of knifefish, refuse to feed on prepared foods at all. This means frozen fish foods, like bloodworm and tubifex, are critical for maintaining them in aquariums.

Knifefish require live or frozen foods and will not eat pellet or flake foods.

However, all fish enjoy a frozen natural food when the opportunity arises. They can supplement prepared diets like pellet and flake foods to good effect, even helping to trigger spawning.

They also represent excellent value for money when compared to live foods. One small bag of live Daphnia may cost between £1 and £2. A pack of frozen Daphnia may easily contain 24 or more servings and cost between £2.50 and £3.50 on average. These frozen foods can also be available in large slabs which represent even better value!

Are frozen foods dangerous?

Frozen foods have none of the problems of live foods, which can introduce diseases from their cultures into your aquarium. Some pathogens can survive freezing. So companies will treat the frozen food to kill any that remain with radiation. Fear not, this food will not set Geiger counters racing or give you or your fish cancer and is perfectly safe.

Frozen foods, however, do need to remain just that — frozen. If they defrost, you will need to use them immediately or throw them away. Do not refreeze your food as bacteria could contaminate your food. Stored correctly, they will remain good for around 18 months.

Live foods like this Daphnia bring with them any diseases from their culture 

Are frozen fish foods nutritional?

Frozen foods are prepared while still nutritious. Aquatic live food, on the other hand, loses nutrients over time. While it is safe to keep a bag of Daphnia in the fridge for a few day, it will slowly become less beneficial to your fish. This is because the creatures have no food during this time and survive using their reserves.

You can actually buy frozen food with added nutrients. For example, we can feed brine shrimp (Artemia) with foods high in vitamins and minerals prior to freezing. When frozen, these foods remain in the guts of the shrimp and the fish get all those beneficial nutrients.

We can even enrich frozen foods further before feeding. You can add a high quality liquid supplement to your food when defrosting it.

Frozen foods are often sold in these easy to use blister packs. Photo by Shutterstock

Related article: What you need to know about hatching baby brine shrimp

How do I feed frozen fish food?

Some aquarists like to thaw for a few minutes prior to feeding. This allows you to split the food across several aquariums. This also allows you to drain off the liquid as it can be high in phosphates which you may not want in your aquarium.

Others prefer to offer a frozen block directly to the tank where it defrosts and the fish pick on the sinking food. This is quick and easy, and usually does not cause any problems to the aquarium. Some reef keepers believe the small bits of food released by using this method feeds filter feeding corals.

Frequency can vary between fish species and some aquarists like to offer one or two frozen 'treats' a week. Others like to feed almost exclusively frozen products — only infrequently supplementing with dry foods.

Whatever you choose to do, feeding your fish has never been so enjoyable. Watching catfish scour the sand for frozen bloodworms is a treat for both you and your fish.

Remember to only feed as much as your fish can eat, and remove any uneaten food.

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