Figure 1.

Schematic representation of the time sequence of the experiment showing the two conditions that differ in the arrangement of the substrate: fluctuating or stable. Rectangles indicate the aquarium floor with small circles representing terracotta pots used to provide cover for animals. In the fluctuating condition, pots were rearranged in either a random fashion or concentrated in the center, edges, or corners of the tank, or there were no pots at all, as shown schematically. In the stable condition, pot arrangement was kept constant. Arrows indicate when the substrate was altered and fish were measured.