male of great diving beetle, dytiscus marginalis, wide-spread freshwater predator insect rest balancing

adult aggressive algae animal aqua aquarium background balancing beetle behaviour biotic biotope bug clear coldwater dangerous decorative display diving driftwood dytiscus eco ecological ecology endemic europe european fauna fish fishkeeping free fresh freshwater great hornwort hunt hunter insect lake legs look macro male marginalis natural nature predator protection rear rest space tank temperate underwater vegetation water weed widespread wild