I would advise against getting an Elephantnose Fish. 90 L is way too small even for just one juvenile fish. Elephantnose's are social and should be kept in a group (6+ or something) which would require a much large tank. They're extremely intelligent fish. They're weakly electric fish and they use electrical pulses to communicate and search for food. Keeping them in a confined space like an aquarium disturbs their ability to communicate properly (the pulses are distorted by the aquarium). For example, elephantnoses can only be sexed by measuring the electric fields put out by the fish, and breeding has never been accomplished in the aquarium possibly because the confined space makes it impossible for the fish to determine each others sex. I read an article recently (I can't find it now), suggesting that Elephantnose's really shouldn't be kept in aquariums at all.