I... What you want to see the level of water if its a Hydroponic system? sorry but Im working in almost the same and I think that what you need is change the water or looking the conductivity and pH, but not the level. In any case if is a full hydroponic system (100% water) what you have to use is a Water level sensor, and in the other hand, if you are ussing a mix of Hydroponic system (sand + water) you can use the moisture sensor that the guys give you... Send me an email if you need help or a PM!