The continuous culture of fresh green algae for use as food for Daphnia magna in toxicity tests is labor intensive. The possibility of using freeze-dried Chlorella vulgaris as an off-the-shelf food was investigated. The performance of D. magna provided with freeze-dried food was investigated over several generations and was found to satisfy the current EC validity criteria. However. a number of life-history parameters, for example, fecundity and neonate size, were significantly reduced when compared to animals fed fresh algae. The effect of freeze drying on cell size and availability are investigated and discussed in relation to daphnid performance.