What you need to know about frozen foods

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Frozen fish foods offer wild source foods in a safe form. They are also great value for money, as Nathan Hill explains.

Frozen food gives us access to cuisine simply beyond culturing in captivity, such as krill and Calanus species. Today, we can offer our fish something very close – if not identical – to what’s found in their natural habitats.

Frozen foods have none of the problems of live foods, which can introduce diseases, and most are treated with radiation before being sold. That’s not to say that this food will set Geiger counters racing or give you cancer, but does mean that any pathogens that could have survived the freezing process — and there are some — will have been eradicated.

Fish food is often the safest, cleanest food in our freezers.

Frozen foods score over live in that they are prepared while still nutritious. If I purchase a bag of live Daphnia and keep it in my fridge for a few days it will start losing much of its goodness as the creatures metabolise.

In some cases, nutrients can be deliberately added, as with brineshrimp which are often enriched prior to freezing — their guts being loaded with extra vitamins and minerals for the fish to then consume.

Frozen foods, however, do need to remain just that — frozen. Once defrosted, they have either to be used immediately or discarded. They cannot be refrozen as this will lead to the production of free radicals and they become toxic as a food source. Stored correctly, they will remain good for around 18 months.

They represent excellent value for money when compared to live foods. One serving of live Daphnia may cost between 50p and £1. A pack of frozen Daphnia may easily contain 24 or more servings and cost between £2.50 and £3.50 on average.

Frozen foods can be enriched before feeding, usually with a liquid supplement. Some aquarists like to thaw for a few minutes prior to feeding, but others prefer to offer a frozen block directly to the tank where it defrosts and the fish pick up on the sinking food.

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

Fish such as elephantnoses require their entire diet to be of frozen or live offerings, but all fish will enjoy a frozen morsel when the opportunity arises.

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