Revolutionary advancement in realizing nanosensors promises unprecedented enhancement of applications in several fields such as health, industry, agriculture, environment, sport, etc. The small size of nano-sensors and their THz band leads to significant constraints in energy, memory, processing, and transmission range. To combat these constraints, recent progress and active research in nano-sensing technology have led to increasing interest in connecting these nano-sensors in a new network technology, the nano-network. Communication in nano-networks still poses a non-trivial challenge owing to the constraint of processing, storage, energy, and communication range capabilities of nano-nodes. Short communication range in the THz band renders direct communication in nano-networks infeasible most of the time. Hence, multihop communication among nano-nodes is currently regarded as the viable solution for nano-network realization. In this paper, we investigate three routing protocols; controlled flooding, CORONA, and Hierarchical AODV. We evaluate the performance of the three protocols with respect to energy consumption and network delay against transmission range and network density.