Hugo kamishi natural gravel fine is 1-2mm in size with a range of colours and shapes to naturally match a riverbed.. The 1-2mm size ensures hugo gravel is a great choice for planted aquariums and provides a great rooting medium.. Suitable for coldwater and tropical aquariums and does not alter the ph.. Features. 5Kg bag. Approximately 1-2mm. Natural gravel. Does not alter ph levels