AbstractQualifying and quantifying nutrient flows within open‐water Integrated Multi‐Trophic Aquaculture (IMTA) systems is necessary to determine transfer efficiencies and to assess overall system performance. There are numerous empirical performance metrics, such as spatially defined growth and nutrient sequestration, which may have application. When used in combination with modelling techniques, empirical approaches can be a powerful tool for system assessment or prediction. Simple empirical growth models, such as the thermal‐growth coefficient (TGC) and scope for growth (SFG), are applicable to aquatic animals and can include nutritional mass‐balance approaches to estimate nutrient loads. Comparable empirical growth models exist for seaweeds. Mechanistic‐based dynamic growth and reproduction models, such as Dynamic Energy Budget (DEB), are more complex, but have application beyond site‐specific empirical models and can, therefore, be included into larger ecosystem models for application to IMTA. Proximity, ecological transfer efficiencies, particle dynamics, species culture ratios and the timing of multi‐species production cycles can have profound implications for IMTA effectiveness and require careful consideration for system assessment. This review provides a pragmatic evaluation of performance measures and models to assess nutrient transfer and growth in open‐water IMTA systems.