I forget who, but someone posted a nice reference on copepods, amphipods etc. with pictures to show you the difference. copepods are usually only 2mm or so, amphipods are a bit larger maybe 5-10mm...so copepods are about the length of the i in shrimp and amphipods are about the length of the word shrimp....both appear shrimp like sortof....it could also be brine shrimp if you have been feeding with live brine shrimp...because some may escape being eaten, hide in the live rock and produce millions of eggs...so this is why you have to be careful using live anything as food. :thinking: