Rotifers form their own Phylum. From the phylum, Rotifera, AlgaGen offers Brachionus plicatilis(L-strain), Brachionus rotundiformis(s-strain). We offer either, both of which are great for breeding marine animals (fish, seahorses). Rotifers will feed numerous corals, larval animals as well as some adult fish. We consider the rotifer to be a gel-cap. What we mean is that a rotifer will swim around and eat small particles which it holds onto for up to 4 hours. After the 4 hours it has minimal nutrition left in its body, in other words, it is only as good as what it eats or has eaten recently. We recommend feeding them to your tank after you have added the PhytoPlankton-again turn off the skimmer for a few hours. Your corals and fish will love them. Build up slowly to frequent feeds but feed as frequently as your budget allows.