Three feeds; fish faeces recovered from a recirculating aquaculture system (RAS), fish faeces combined with watercress roots (Nasturtium officinale), and a commercial pelleted feed formulated for pike-perch, were fed to European Noble crayfish (Astacus astacus) (average initial body weight ± SD was10.7 g ± 3.5; average initial body length ± SD was 3.1 cm ± 0.4) for 84 days at excess daily rations. Crayfish fed with the pelleted fish feed exhibited significantly (P < 0.05) higher mean final body weight ± SD (FBW, 13.84 g ± 1.24) compared to animals fed fish faeces (11.14 g ± 0.47) and those fed the combination of fish faeces/watercress roots (12.91 g ± 1.99). Mean final body length (FBL) and survival were also significantly higher in animals fed pelleted fish feed than all other treatments (P < 0.05). Faecal macronutrient contents (28.5% crude protein and 2% lipid) are within required dietary range of A. astacus, indicating poor growth performance was not related to quantitative faecal macronutrient composition. The lysine and methionine content of faecal waste was 13.1 g kg−1 and 3.8 g kg−1 respectively. The methionine content of the faecal waste was therefore considerably below (60% below requirement) the requirement for crayfish. Amino acids known to stimulate feed intake in crayfish were about 50% lower in concentration in faeces compared to concentrations in pelleted fish feed. The concentration of taurine was below detection limit in faeces. It is hypothesized that unsuitable amino acid composition and/or limited ability to handle faeces explain low growth and survival rates in A. astacus fed fish faeces and the combination of fish faeces/watercress roots. Graphic Abstract: [Figure not available: see fulltext.]