A magnetic support (10) for aquariums includes a first and a second support element (20a, 20b), each of them having a magnet (26a, 26b) so that by coupling the first and second support elements (20a, 20b) by interposing an aquarium wall (50) between them, the attracting magnetic force operating between the two magnets (26a, 26b) locks the two support elements (20a, 20b). Each support element (20a, 20b) comprises a flat element (40a, 40b) made up of flexible material having a peripheral projecting lip (46a, 46b), so that when the two support elements (20a, 20b) are coupled together by interposing the wall (50), the peripheral projecting lips (46a, 46b) are flattened against the wall (50), thus creating a suction effect.