Companies selling copepods are extremely common in Europe and the US and I sometimes find myself wondering why. They certainly serve an important purpose, but Ive always had to scratch my head and wonder why theyre such a popular product on the own when buying live rock either maricultured or wild collected would introduce a wider variety of species than buying bottles of 5 species at most. The price of buying the copepods separately would almost cover the cost of the live rock but add fewer species, which appears to be a big way companies try to entice customers (mixed copepod species sold in bottles or bags seem to sell for even higher prices). Wouldnt it make more sense to buy live rock and introduce many species without buying them separately? Dose phytoplankton for a week or two and your tank will be crawling.