Secondary grazers

Secondary grazers concentrate this primary nutrition in their tissues by preying on the smaller organisms. They include rotifers, which may in turn be among the first foods of the larger kinds of fish fry. More commonly, though, rotifers are eaten first by a crustacean, such as a copepod (Cyclops, for example) or a cladoceran (such as Daphnia or Moina). Flatworms and nematodes, which range down to microscopic scale, also rank among the secondary grazers. For more detail, look into the "Biofilm" and "Plankton"sections in the menu at the left.
 
Minor players. Some other invertebrate organisms in our aquaria play minor roles in the food web. Hydra are a possible menace to very small fish fry, but they don't play a major role in the food web. Few fishes will eat hydra, so ordinarily the food web culminates here; but the hydra in turn may be eaten by a gourami or Macropodus opercularis. And other minor players such as mites and springtails, can be found among the aquarium's visitors in the "Invertebrates"section.