Question 1

What is the general rule for sizing a hydroponic reservoir?

Accepted Answer

A common rule is 4–7 litres of reservoir volume per plant for small crops like lettuce, and 10–15 litres per plant for large fruiting crops like tomatoes. Larger reservoirs buffer temperature swings and EC/pH drift, reducing how often you need to top up and re-dose.

Question 2

How often should I refill my reservoir?

Accepted Answer

Top up with plain pH-adjusted water as the level drops (typically daily in summer). Do a full reservoir change every 7–14 days to prevent salt buildup and pathogen growth. DWC and Kratky systems may need topping up daily during peak growth.

Question 3

Why does the recommended size include a 50% buffer?

Accepted Answer

The buffer accounts for evaporation, plant uptake variability, and the dead-zone volume at the bottom of the tank that pumps cannot access. A larger reservoir also stabilises temperature and reduces EC and pH swings between nutrient top-ups.

Reservoir Size

Reservoir Size