Unless the aquarium is a reef with corals only, then there are going to be fish present. Whatever species these fish are there will not be sufficient food in the aquarium to meet their needs.
One of the most pleasurable parts of keeping a marine aquarium is feeding the fish. Maybe this is because there is direct interaction between the fish and the aquarist. There are a few fish that have real characters and become pets individually, but most fish only respond to movement outside the aquarium as, after time has passed since their introduction, it triggers their food response. They come to the front of the aquarium – ‘Where is it then?’
Marine fish need more than just ‘some food’. They have evolved to eat a particular type of food on the wild reef, or they are omnivores. Having said that, most fish will respond to any food once they recognize it as food. This recognition may initially come from their tank mates’ reaction.
Marine fish need to eat generally what Mother Nature intended. This could be algae which is a good example as some fish, for example surgeons, need it to remain healthy. So the aquarist cannot simply decide that a particular food is good and sufficient simply because the fish eat it.
One of the best base or foundation foods is flake. Flake is formulated by nutritionists to generally supply all the protein etc that marine fish need. This doesn’t mean to say that this is all the fish get; the diet needs to be varied.
Most aquarists use frozen foods as a variation as it comes in all sorts of guises, either mixtures or particular types. Two types that are very popular are brine shrimp, preferably ‘enriched’, and mysis. I use them myself in addition to other types including flake.
Flake as said is produced to generally meet the needs of marine fish and can be said to be nutritious. What of frozen foods though?
Using frozen food is straightforward as it usually comes in blister packs that the aquarist can store in the freezer. Getting it ready to feed the fish is also easy, all that needs to be done is to release one blister, if necessary reduce the amount by cutting it when still frozen, and then place it in an egg cup or similar. After a little RO (reverse osmosis) water or seawater from the aquarium has been added the food thaws quickly. Frozen food should not be thawed in a microwave as it has been anecdotally reported that this reduces the nutrition value.
So the question about the food being handy for aquarists has been answered – it certainly is. But is it nutritionally good for the fish?
I am not qualified to talk about nutrition. However, I can sensibly speculate and turn to human frozen food to do so. I used to wonder if frozen food for our consumption would be as good as the fresh variety. I used to assume that it wasn’t, as surely fresh food must be best! However, nutritionists state that the answer depends on the age of the food when it was frozen, if it was lying around or in transit for a good period the nutritional value would decrease. If the food was frozen immediately or nearly immediately then the nutritional value would be equal to fresh or even better if the fresh type had been harvested a while ago.
So perhaps this could be applied to frozen fish food. When were, for example the brine shrimps, frozen? I would imagine that there will not have been much delay in applying the freezing process as shrimps of that size are not suitable for keeping out of water and when in water they would have been living. The same would apply for other types of ‘live’ frozen food. If the food was frozen immediately the nutritional value shouldn’t have deteriorated. The question of what food value existed pre-freezing, that is when in its live state, is another matter. Brine shrimp and similar are not said to be particularly nutritious though there is obviously nutrition present. They are also said to give valuable roughage. Sometimes they are sold as ‘enriched’ which means the shrimp were fed a rich diet, which should be reflected in the frozen state if the freezing process was not delayed.
There are other frozen foods besides shrimp varieties and I would guess that the same applies, when were they frozen?
I feel fairly certain that a nutritionist knowledgeable in this area would have a lot more to say. However, the consideration of ‘when was it frozen’ would seem to cover the basics at least.