Is it true that some cichlids should not be fed ‘bloodworm’?

Yes, this is correct. All South American cichlids including dwarf cichlids will relish on the idea of feeding on bloodworm, so for these guys it’s safe to use. Cichlids from the great African Lakes on the other hand are very inefficient in digesting hemoglobin. Bloodworm is full of hemoglobin which give the worm its specific color The hemoglobin appears to irritate the fish’s gut and a condition known as ‘Malawi’ bloat may occur. In general, these fish thrive on minuscule food particle that they find in the ‘awfuch’ (plankton and inverts found in the algae growing on the rocks). But you should try feeding your African cichlids Cyclops or you will see the feeding response for yourself.