Hydroponic Reservoir Size Calculator
Calculate the minimum reservoir volume for your hydroponic system from plant count, growth stage, and system type.
Prevent nutrient fluctuations and dry-out.
Why reservoir size matters in hydroponics:
An undersized reservoir causes rapid pH swings, nutrient concentration spikes, and temperature fluctuations — all of which stress plants. A properly sized reservoir stays stable between changes and gives you a buffer when life gets busy.
General rule of thumb:
Minimum reservoir = Number of plants × Gallons per plant
Gallons per plant by system type:
| System Type | Gallons/Plant | Notes |
|---|---|---|
| Deep Water Culture (DWC) | 3–5 gal | Each bucket IS the reservoir |
| Ebb and Flow (flood/drain) | 1.5–3 gal | Shared reservoir, cycles 3–4×/day |
| NFT (Nutrient Film) | 1–2 gal | Continuous thin film flow |
| Drip system | 1.5–2 gal | Timer-controlled drip emitters |
| Kratky (passive) | 2–3 gal | No pump — jar method |
| Aeroponics | 2–3 gal | Misted roots, high evaporation |
Worked example:
12 tomato plants in an Ebb and Flow system at 2.5 gal/plant:
- Minimum reservoir = 12 × 2.5 = 30 gallons
- Recommended (add 25% buffer): 37.5 gallons → use a 40-gallon tote
Growth stage adjustment:
Mature, large plants (flowering tomatoes, peppers) drink 1–2 gallons per day each in hot conditions. Seedlings use a fraction of that. Start conservative and watch your water level — if the reservoir drops more than 25% in a day, you need a larger one.
Temperature control:
Larger reservoirs are easier to keep cool. Root zone temperature should stay between 65–72°F (18–22°C). Above 75°F, dissolved oxygen drops and root rot (pythium) risk skyrockets. In warm environments, add a water chiller or use frozen water bottles.
Practical tips:
- Use opaque containers — light promotes algae growth
- Never let the reservoir run dry — exposed roots die within hours
- Top off evaporated water with plain pH-adjusted water, not nutrient solution (this prevents salt buildup)
- Full reservoir changes every 7–14 days keep things stable