For the needs of the EU MFSTEP project, and based on the experience gathered during its previous phase, various experiments have been planned to prevent biofouling of the optical instruments on the Mediterranean Moored Multi-sensor Array (M3A). Although the system, when operational, is deployed in oligotrophic open sea waters 22 N.M. north of the port of Iraklion Crete, severe fouling prevented the proper functioning of the optical sensors and sources after 30 days of deployment. These experiments are still underway, however, emerging initial results from a 50 day deployment in coastal waters, indicate that the introduction of a bromine canister and copper tubing in the flow system can result in almost fouling free instruments.