How often does water need to be added or changed?
It is important that you keep enough nutrient solution in your reservoir so that the submersible pump stays completely submerged.
During cool months, add nutrients to the water every time you fill your reservoir tank. You can mix water and Tower Tonic in a 5-gallon bucket prior to adding it to the reservoir (100ml of each Tower Tonic A and Tower Tonic B for each 5 gallons of water). During hot months, add nutrients every other time you fill your reservoir tank.
Repeat the process if more nutrient solution is required.
Depending on the outside temperature and crop types, a full reservoir typically lasts 2-3 weeks. During the hot months, your plants will use nutrients and water much faster. Do not let your tank drop down more than half way.