Once it has been decided that the experimental design requires the use of living organisms, researchers have ethical obligations to maintain organism health and to reduce organism stress where possible. This can be a challenge to some physical scientists and engineers not used to biological problems. But there are also challenges for some biologists and ecologists who may not be familiar with how environmental conditions in a laboratory flume area controlled. Physical scientists often assume that small or neurologically simple organisms, such as worms and other invertebrates, do not need to be looked after or do not have the complex responses to stimuli that are evident in larger, vertebrate animals. These assumptions are erroneous. Small organisms and plants suffer stress like any other and attention should be paid to their well-being. Similarly, these organisms interact with the physical environment in complex, subtle, but, often important ways. Consequently, organism husbandry and the conditions provided during experiments have an impact on the behaviour and physiology of small organisms and therefore on their interactions with flow and sediment that must be considered when designing them. Therefore, husbandry has two concerns: providing conditions that are not only ethical but also ensure that behaviours are analogous to wild equivalents. The following chapter emphasises the complexity of organism husbandry and the need for suitable knowledge of the organism(s) being used. It is designed to act as both a source of information for physical scientists interested in researching the hydraulic effects of organisms and for biologists and ecologists seeking a clearer understanding of the constraints presented by experimental hydraulic facilities.