Reservoir Management Basics
A well-managed reservoir is the foundation of stable hydroponic production. The key principle is that plants consume water and nutrients at different rates — water is consumed faster, so EC rises as the reservoir depletes. Understanding this prevents over-feeding when topping off.
Accurate EC and pH meters are non-negotiable for reservoir management. These are the most reliable options at each price point:
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Frequently Asked Questions
How do I calculate how much nutrient solution to add to my reservoir?
Determine your target EC, current EC, and current volume. First calculate the dilution from top-off water: new EC = (current EC × current volume) / target volume. Then calculate additional concentrate needed to reach target EC. Our calculator does this automatically — just enter your values.
How often should I top off my hydroponic reservoir?
Top off with plain water when the reservoir drops by more than 10–15% of its total volume. As plants absorb water faster than nutrients, EC naturally rises between changes. Add water to bring the volume back up, check EC, and add concentrate only if EC has dropped below target. Full reservoir changes every 7–14 days are recommended for recirculating systems.
Should I add water or nutrient solution when topping off?
Almost always plain water. Plants use water faster than nutrients in most growth stages, so EC rises as the reservoir depletes. Adding more nutrient solution when topping off increases EC further. Add plain water first, measure EC, then add a small amount of concentrate only if EC has dropped below target.
What pH should my hydroponic reservoir be at?
For most hydroponic systems, target pH 5.8–6.2. This range allows optimal uptake of all major and minor nutrients. Below 5.5, calcium and magnesium become less available. Above 6.5, iron, manganese, and zinc availability drops. pH naturally drifts as plants metabolize nutrients — check daily in active systems.
How big should my reservoir be?
A commonly recommended minimum is 4 liters per plant for small systems, 10–20 liters per plant for larger setups. Larger reservoirs buffer EC and pH fluctuations — a 100L reservoir with 4 plants is far more stable than a 20L reservoir with the same plants. More volume reduces maintenance frequency.