Colored ceramic foams with tailored pore size and surface functionalization used as spawning plates for fish breeding

The growing demand for reliable porous substrate materials for aquaculture of marine ornamental fishes (i.e. substrate spawners) requires a controllable processing in combination with a straightforward functionalization to adjust both, the material properties and the surface physico-chemical characteristics. In this study, highly porous ceramic foams made of alumina obtained by direct foaming are presented, which are conditioned for controlled aeration of egg clutches laid by clownfishes serving as model organisms for marine substrate spawners. Increasing stirring velocities during preparation of high alkane phase emulsified suspensions (HAPES) lead to decreased µm-scaled foam pore sizes, while similar high open porosities of around 80% are achieved. Wet-chemical silanization using hexadecyltrimethoxysilane (HDTMS) followed by subsequent oxygen plasma treatment of the foam surface is applied to generate bifunctionalized foams with hydrophobic matrix and hydrophilic surface properties. Under marine aquarium conditions, external aeration through the hydrophobic matrix of the foam is applied marginally below bubble point pressures resulting in a significant increase of the dissolved oxygen concentration of the surrounding water close to the foam surface without formation of undesired air bubbles. In accordance with increased foam pore sizes oxygen saturation rates of 0.26, 0.49 and 0.85%/min are obtained ensuring high oxygen concentrations at the spawning plate within a few hours. Assemblies of five bifunctionalized spawning plates to a ceramic housing are accepted by clownfish pairs, laying their eggs directly on the aerated ceramic substrate. The presented spawning plates are highly promising for sustainable aquaculture of marine ornamental fishes aiming to improve the survival rate of early life stages.