<p>The climbing and attachment behaviour of sea cucumbers (<i>Holothuria tubulosa</i>) on the sidewalls of aquaculture tanks was investigated to identify the key factors influencing this behaviour and its potential implications for aquaculture. The effects of size class, stocking density, ambient light regime, biofilm presence, and water level on wall-climbing behaviour were analyzed using digital video monitoring of <i>H. tubulosa</i> under temperate conditions. The results showed that juveniles exhibited significantly more climbing behaviour than adults. A significant linear relationship was observed between stocking density and climbing activity, with the highest rates recorded at 12 and 24 juveniles/m² under both light and dark conditions. Increasing the water level from 10 to 20&#xa0;cm above the sediment also led to a greater number of sea cucumbers climbing the tank walls. Notably, the presence of algal biofilms stimulated wall-climbing as a foraging response. Among the variables examined, biofilm presence, size class, and stocking density emerged as the most influential factors. Understanding these behavioural drivers can help optimize aquaculture practices and reduce the negative impacts of wall-climbing on the growth performance and welfare of cultured sea cucumbers.</p>