The substrate should be comfortable and in case you decide to put rocks be certain They may be clean river rocks. They get their name from their fins, paying homage to a hippopotamus’s ears. They’re also identical in physical appearance on the animal, which has a thick and stubby bodies. https://aquariumshops.law.blog/2025/02/11/4-questions-to-ask-while-interviewing-a-pond-cleaner/