The importance of quality ingredients in fish feeds

Poor formulation in fish feeds can lead to incorrect quantities and low-quality ingredients being used, which can affect the health of the fish in an aquarium or pond but will also have significant impact on water quality.

Why is fish food so important?

When directing customers on how best to look after their fish, many retailers will advise “you are not looking after the fish, you are looking after the water”. This is because one of the main additions to the aquarium’s water supply is food – aside from oxygen, décor and plants – the food will impact the water significantly.

The quality of the food determines how much of it is eaten, how much of it is wasted (in terms of small and therefore non nutritional particles such as dust), and importantly how much is utilised by the fish, verses what will be passed through as waste. Unlike our furry friends, we can’t pick up the waste produced and a poor-quality diet will lead to water quality deteriorating quicker, increasing the need for maintenance and cleaning.

It’s fair to say this is something a high proportion of consumers dislike the most about fishkeeping. This can, eventually, in the worst-case lead to increased fish mortality, something we all want to avoid.

As humans we have become more and more aware of good diets and the effects of poor ones, this increased education is great as it enables us to speak to customers about their fish’ diets in a way that will resonate more.

Vital energy sources

Carbohydrates are the principal source of energy in the normal diet of humans, in fish however their use as an energy source is much more variable. Generally, those species with a carnivorous diet are poorly able to utilise carbohydrate as an energy source, hence a carb-rich diet will pass out of the fish undigested, leading to polluted water.

Omnivorous species are better able to break down polysaccharides like starch liberating the glucose subunits, though there is still much variability. With so many species available to us it’s important to understand that different fish need different diets to thrive. For example, carbohydrate digestibility in goldfish (Carassius auratus) is around 70% but for moonlight gourami (Trichogaster microlepis), the figure is closer to 50%.

So, if a customer comes to you for advice about water quality, it might be worth digging deeper into what species they keep and what diets they are feeding, with a view to identify if diet is contributing to poor water quality.

Proteins are another possible energy source for fish, these large organic molecules are built from building blocks known as amino acids. Fish are able to utilise proteins for energy much more effectively than mammals, however when formulating a diet for fish the nutritionist is incentivised to minimise the fraction of protein used for energy.

This is partly because the breakdown of proteins liberates ammonia, a chemical all-too familiar with fishkeepers, so again it’s worth asking about fish feed when discussing ammonia levels with your customers.

Essential amino acids

There are 20 different amino acids found naturally, 10 of them are essential to fish, meaning they cannot be synthesised in the body and must be obtained in the diet. The combinations of these 20 amino acids is vast, giving a huge range of different proteins found in nature.

When a protein is digested it is broken down into its constituent amino acids; feeding fish exclusively on a protein source which is deficient in one of the 10 essential amino acids will inevitably lead to malnourishment.

If a customer comes to you concerned about the health and nourishment their fish are receiving through the feed it would be worth advising them to feed a diet containing good quality fishmeal. Fishmeal – the ground up remains of fish too small to be directly consumed by humans, or by-products of fish – is the traditional protein source for many fish feeds.

Feeding fish on good quality fishmeal should provide the essential amino acids that fish require and the amino acid profile of fishmeal is very good, compared to other sources of protein. With this in mind, all Tetra products are made using the highest quality protein sources.

One to watch: a fish diet can have the required level of protein, but the quality of the protein can be inappropriate.

The digestibility of a protein relates to its structure and function; tough structural proteins are poorly digested for example. Fishmeal derived from herring was 92-95% digestible in the rainbow trout whereas ‘feather meal’ a waste product of the poultry processing industry, (clearly a much cheaper protein source than fishmeal!), was between 52 and 87% digestible in the same species.

If fish are fed a high proportion of indigestible protein in their diet, then the fraction passing out in the faeces will be higher and the subsequent pollution of the aquarium or pond water much worse.

Crucial vitamins and minerals

Vitamins are organic compounds required in small doses for specific physiological functions, vitamin A is required for the production of the pigments in the retina required for vision, vitamin K is required for blood clotting and vitamin E is an important antioxidant. Vitamin C has many different functions, bone calcification, iron metabolism and collagen formation.

Vitamin C deficient fish show malformed spines, gills and gill covers due to the lack of collagenous connective tissue. Vitamin C is also vital in proper immune system function; one study showed that Pacu (Piaractus mesopotamicus), fed a vitamin C deficient diet had significantly more gill fluke parasites following experimental challenge than those fish in a parallel system fed vitamin C.

Minerals are inorganic elements required by the fish in small doses for various specific functions. One of the most important minerals is phosphorous which is required for production of DNA, cell membranes and numerous other functions.

The amount required in the diet is small but variable with species; carp require a phosphorous level of 0.6% for example. The plant and animal-based ingredients in the food should supply plentiful phosphorous to the fish, however the ingredient source can affect phosphorous availability. Plant-based sources, (especially grains), contain the compound phytate which chelates phosphorous in the food rendering it unavailable to the fish.

Ensuring fish get the optimum diet should be the priority when creating a diet. With this in mind Phosphate is something that, when in the water, can lead to other problems and while it would be easy to remove a large part of it from the diet this would be unfavourable.

Overall, explaining the key benefits of a quality fish food to your customers will give them a far better and arguably easier fishkeeping journey, and in turn the fish will be healthier and thrive. This will ensure you are recommending products that work, gaining trust and making sure your customers are long term fish keepers, experiencing less problems with fish that are happy and healthy.

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