You can run the system hydroponically with a good full spectrum organic hydroponic nutrient solution such as Espartan. However, this is a more expensive way to run the system in the long haul as opposed to feeding fish who provide nutrients naturally and consistently. Fish feed is less expensive and nutrient delivery is more stable and consistent with fish than it is with periodic dosing of hydro nutrients. That said, you may find running the system initially with a low dose of organic hydroponic nutrients can help get your plants up and thriving until you are able to get your fish delivered. We do not recommend using conventional hydroponic nutrients in an aquaponic system because they may not be safe for fish. We have successfully used Espartan in certain instances in our aquaponic system without fish. Once you are ready to add fish, be sure to not add any more Espartan and test the ammonia and nitrite levels in the water to make sure they are at safe levels.