bitterling male in bright spawning coloration, monkey goby relax on sand bottom, freshwater wild caught domesticated fish

adult amarus animal aqua aquadesign aquarium aquatic behaviour biotic biotope bitterling brackish captive clear closeup coldwater conditions controlled cyprinidae decorative dominant driftwood ecology ecosystem endemic european explore fauna fish fishkeeping fluviatilis free gobiidae hobby ichthyology interaction juvenile line look macro nano natural nature neogobius peaceful pontocaspian protection research rhodeus space spawn tank temperate threat underwater water widespread wildlife