Why should you feed mealworms to your fish?

Mealworms as part of a fish’s diet

This blog will be looking at multi factorial benefits of including homegrown mealworms to your fishes diet. A brief discussion on feeding mealworms to pond, tropical and saltwater fish will finalize this blog.

It is well established in the aquarist community to include insects in the diets of the fish they keep, with bloodworm, daphnia and other livefoods commonplace. These have been used for fish whether that be dried frozen or live, and for good reason, many of the fish that are popular to keep today are carnivorous or omnivorous so giving them a diet resembling  what their wild counterparts would eat is widely considered good for them.


Most commercial fish foods available contain fish meal, which although a nutritionally superior option it is not without its flaws, food waste can be an issue for your tank or pond. The financial implications and environmental impacts the huge use of fish meal in commercial foods has pushed the market to look at alternatives. This means there is lots of research that has been done in recent years on insects (including mealworms) being used as an alternative source of proteins and fats for fish, while these studies are on commercially reared fish species the findings can still be used to aid aquarists, confirmation they can feed a more natural diet whilst still keeping their fish in the best possible condition.

While shown In these studies a diet based solely on insects does lead to a reduction in growth rate,  more positively a 25-50 % supplementation of insects (depending on species) leads to an equal or higher growth rate and an indication of good health. One study on African catfish found that with a higher than 50% insect based feed they still did well, with it also being noted that the mealworms were more palatable to the fish than the fish meal based food. Although not fish, a study done on white shrimp also tested immune response, which when fed up to 50% insects as part of their diet were higher than those on fishmeal based diets only. The studies showed that those with more than just fish in their aquarium can benefit all their aquatic occupants with the addition of insects to their diets.

Whether you own koi, cichlids or a communal tropical tank growing mealworms for your fish could be of benefit to you and your fish. Growing your own mealworms is simple and for those who are worried about disease transmission when feeding live foods, it makes the food you feed a closed system and you are in complete control of what they are fed on and the conditions that they are being kept in. You can still freeze or dry them yourself if that is your preferred way of feeding. Unlike daphnia and brine shrimp which are also easy to grow at home mealworms cater for a larger variety of sizes of fish, cutting up small ones for the very small fish and feeding the larger ones whole to the larger fish.

When growing your own it can also be advisable to feed freshly moulted (having just shed their own skin) to make them more digestible minimizing the chitin (exoskeleton) content. Mealworms can be fed as a single insect source as well as in addition to those you may already grow yourself. Feeding the mealworms on a feed with good nutritional content will mean the mealworms will also be of better nutritional content for your fish and this can be boosted further by gut loading - feeding specific foods to the mealworms just before harvest.


Fish Pond


 Mealworms for koi and other pond fish

Koi can be expensive and many keepers have a real passion for the fish they keep, this makes them cautious as to what they feed them and the care they give them, wanting the very best for the fish in their care. Mealworms are a nutritious treat for koi, a good source of protein and many other nutrients. They are also high in fats which can be beneficial to young fish but does mean it should be fed more in moderation for mature ones. Gut loading the mealworms prior to feeding will further increase the nutritional benefit. Although most koi enjoy dried, feeding live is a good source of behavioral enrichment as well nutritional. It is important to note they should only be fed as supplementary feed, too much too often and the fat content can become a problem as well as the exoskeleton which is difficult for the fish to digest ( this can also be reduced by feeding mealworms that have freshly shed before the exoskeleton hardens)  and only in the warmer months.


Mealworms for tropical fish

Particularly with a communal tropical tank it is important to rotate feeding of a wide variety of foods along with the commercial complete diets so all occupants nutritional needs are all catered for. Mealworms can be a great addition to this varied diet and many of a mixed tanks occupants will enjoy taking advantage of this nutrient rich food source, however they may need cutting up to a size suitable for the smallest resident of the tank. Mealworms are a good source of protein, fats and many other nutrients and most fish will really enjoy them as a new food source. Cichlids especially are insect lovers and as opportunistic eaters gain enrichment from insect sources in their tank.


Mealworms for saltwater aquarium fish

There is very little research that has been done on insect based diets in marine aquarium fish. One done on clown fish did indicate no adverse effects when a lower percentage of the food was replaced with insect based (black solder fly larvae) but at a higher level there was some potentially harmful long term affects, with this in mind it would be advisable due to the delicate nature of these aquariums and their occupants to feed as only an occasional treat.