Red blood worms are the ideal food for strengthening fish. Larvae of the chironomids (nonbiting midges) sometimes occur in masses and form a main food source for very many fish species in the wild. They are NOT the larvae of mosquitoes (Culicidae)!
Ideally you should find a staple food for your ornamental fish, e.g. JBL PRONOVO BEL and supplement it with a second staple food such as JBL PRONOVO COLOR. In addition, use alternating treats and supplements such as JBL PRONOVO SPIRULINA or JBL PRONOVO FIL, FEX, DAPH or ARTEMIO. This ensures a varied diet for the fish in your care.
Food size/mouth size:
It may sound obvious, but it is important that the food size fits the mouth size of the fish. Not all fish are able to bite off larger chunks of food. The fish size to which the food size fits is written on all JBL food tins at the bottom left of the front of the labels.
There is hardly a freshwater fish that will not eat red blood worms unless they are too big for its mouth (e.g. the neon tetra). East African cichlids from Lake Malawi and Lake Tanganyika should NEVER be fed red mosquito larvae. For reasons still unknown, they do not tolerate red mosquito larvae. White or black mosquito larvae, on the other hand, do not pose any problems for the cichlids from the two lakes.