Raising mealworms for the aquarium

The Yellow mealworm (Tenebrio molitor L.) is highly appreciated by a wide range of different fish species and it can also be used to feed frogs, turtles, lizards and other small and medium sized reptiles. Even your birds will cheer if you feed them this versatile and nutritious worm. The larvae are ideal for feeding small creatures, while the adult animal grows to a nice snack-size for larger pets. Raising Yellow mealworms at home is not difficult and will provide you with a constant source of disease-free live food for your fish.

  1. Start by obtaining two rearing boxes. They can be of wood, plastic, glass etcetera; the important thing is that they are well ventilated. The size of the boxes will depend on how much mealworms you wish to cultivate, but they should be around 5 inches deep. You need two rearing boxes since you have to place eggs, larvae and beetles somewhere when you clean the first box. Each box will need a tight fitting lid (preferably with a screen to provide ventilation) to keep other insects, e.g. cockroaches and moths, out of the mealworm culture.
  2. Obtain a mealworm culture. Mealworm cultures are sold by fish shops, pet stores and zoos. If you fail to locate a seller, contact your nearest aquarium club. If possible, get a mixed culture than contains eggs, larvae and beetles since this will speed up the process and provide you with fish food sooner.
  3. Put a 1-2 inches thick layer of chicken laying crumbles over the bottom of the culture box to serve as a food source for your mealworms. Chicken laying crumbles are popular among mealworm growers, but if you fail to locate any chicken laying crumbles there are many other types of food that you can give your mealworms. They will eat virtually any type of dead and decaying animal and plant matter, including cereals, flour, cornmeal, grains and meat scraps.
  4. Place a shallow tray inside the culture box and add a cut fruit or vegetable. This will provide the mealworms with a constant source of water. You can use anything from apples and oranges to bananas and potatoes. Some growers prefer to add a moist sponger or rag instead.
  5. Add the mealworms to the box and wait. Their life cycle is 3-5 months, depending on temperature and access to food and water. They can molt up to 20 times as larvae. Regularly check the culture to see that the fruit/vegetable is still moist and that no insects have managed to get inside the box from the outside. When crumbles has turned into a mixture of fine debris and excrement, add more crumbles. Adding one cup of crumbles weekly is enough for a big culture.
  6. Once the culture has become big enough for your needs, you can start harvesting larvae and beetles. Do not remove too many adults, since this will decrease your future supply of mealworms.
  7. Sooner or later, the culture box will be so full of debris and excrements that you need to clean it. This is when you second box comes in handy. Remove part of the debris, which will contain eggs and larvae, to your second box and add chicken laying crumbles. Clean the first box and add new chicken laying crumbles. One the second box has become well established, simply remove some of its debris (including eggs and larvae) to the first box. If you do not clean out and change the debris regularly, the culture can develop a really strong smell of ammonia.

If you want to loose as few larvae as possible during the changes you can put the debris through a screen of suitable mesh size before you discard it. A more advanced method is to place the debris in a funnel under a light bulb. The mealworms will try to get away from the heat and work their way as far down as possible. This will cause them to fall out of the funnel and you can easily collect them in a new container.

Ants can get inside the culture boxes and harm the mealworms. One way of avoiding this is to place each container on four legs, and place each leg in a water filled jar. You need to refill the water regularly. Also avoid placing your culture boxes next to a wall or anything else that the ants can use to get into the boxes.

A tight fitting lid is necessary to keep moths out of the culture. Cultivating moths is not a good idea, because if they escape from the box they can attack and destroy your clothes, especially clothes made out of natural materials.

Mites are not harmful to your mealworms and will only eat the debris.

Fruit flies
When using fruits as a source of moisture, it is easy to involuntarily introduce fruit flies to the culture. This is actually not a problem, because fish loves to eat fruit flies and their larvae. Cultivating mealworms and fruit flies together will only provide your fish with more variation.