Frozen foods are one of the most popular dishes, preserved in the best possible form for aquatic livestock. It tastes, to our pets, just as good as live food and is also a good substitute for those live foods currently unavailable at our local aquatic retail outlets.

As mentioned previously in one of my articles, my Weather loaches had a preference for worms such as glass worms, bloodworms, tubifex, earthworms etc. Glass worms and tubifex are not available all year round so the frozen versions of these worms are fed as an alternative to the real thing, which my Weather loaches still happily accept. In addition to this my African Clawed Toads, African Dwarf Clawed Toads and Axolotls love tubifex and they are fed on the frozen versions as well.

As some of my friends have cast doubts on the reliability of common frozen foods I decided to do some research on this matter and explain my findings. During my spare time have been travelling around, phoning around, writing to and e-mailing fellow aquarists' gaining advice on the reliability of frozen foods, also doing my own research in conjunction to contacting others.

The issues of frozen foods

Frozen foods will kill pathogens but many pathogens can also form spores which are resistant to freezing. Although the risk is small an introduced pathogen could cause disease in livestock.

Another matter is that bacterial problems are also associated with frozen foods. This does not come from the actual freezing process itself, but from the fact that every time the food is moved from one place to another e.g. from wholesaler - to retailer - to aquarist (and despite all precautions taken), there is a very slight defrosting of the food, and this causes bacteria.

Another concern, and a much debated issue for a long time, is tubifex. I myself have fed live, frozen and freeze-dried versions and have never encountered any problems. This is because my suppliers have, so far, been reliable. The problem with tubifex is that these worms are collected from very dirty areas and carry bacteria and viruses. This is why there are now frozen, freeze-dried and gamma-irradiated versions of tubifex.

Other tips

According to my experience with frozen tubifex in particular, it can make a mess in the aquarium (mainly causing cloudiness) when it starts to thaw and when a feeding frenzy occurs in the tank - because this food is well loved by many fish and other aquatic livestock. But if you have a good-strong filter then this shouldn't be a problem. In smaller aquariums frozen tubifex can cause more cloudiness in water so I prefer to feed either half a tube of frozen tubifex or turn to the freeze-dried form (depending on how many animals are in the tank and how much food they need). For example in one aquarium I have a small number of fish so half a tube of frozen tubifex is fed while the other tank has more fish residents so I feed freeze-dried tubifex to minimise the mess as a result of feeding tubifex.

Another tip is when a weekly water change is due in my aquarium, I feed frozen tubifex and after the fish have fed, a water change is performed as that way I get to carry out the weekly maintenance and to siphon out the mess produced by the tubifex. This action also removes the cloudiness as well.

If you are still worried about frozen foods introducing health risks in your aquarium, then you can feed freeze-dried foods which are a good substitute such as krill, daphnia etc. But too many dried foods can constipate fish so you can also try Gamma-frozen foods - which are the best alternative. I myself feed only freeze-dried tubifex and bloodworm to smaller fish, and not any other dried food, due to the reason mentioned above.


During the many years I have fed frozen foods to my aquatic livestock have never come across any problems. Gamma-irradiated frozen foods, which some of my friends strictly feed to their fish, are mainly for marine species, but can be used for non-marine aquariums such as freshwater tanks housing goldfish. At the end of the day the aquarist must make the final decision as to which form of foods to feed but, as we have seen, frozen foods continue to play an important role in the diet of aquarium fish and my personal opinion is that this form of food carries very little risk to our 'finned friends' and other aquatic livestock.

By Majid Ali, Ryedale Aquarist Society

Thank You Majid Ali for allowing us to use your article.



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