Home hydroponics guide: the numbers to check every day
pH, EC and temperature ranges for lettuce, a five-minute daily routine, and common beginner mistakes, from real growing.
Published
Lettuce in a water system (hydroponics) is easy to grow at home, but whether it thrives or wilts depends on a handful of numbers. This guide sums up what to check every day, the ranges to aim for, and what to do when a value drifts, from real growing at the Baan Rak Phak farm in Saraburi, Thailand.
What to measure, and the right ranges
The drawing above shows the ranges that suit lettuce; the green band is the zone to stay in.
| Value | Good range | If too low | If too high |
|---|---|---|---|
| pH | 5.5–6.5 | add pH-up a little at a time | add pH-down a little at a time |
| EC (growing) | 1.2–1.8 mS/cm | add equal amounts of A and B | add plain water |
| EC (seedlings) | 0.8–1.2 mS/cm | add nutrient a little at a time | add plain water |
| Water temperature | 18–24°C | rare in a hot climate | shade the tank, insulate it, aerate the water |
| Air temperature | 18–28°C | shelter from cold wind | shade net, misting, ventilation |
These are typical figures for lettuce; other crops need slightly different values.
A five-minute daily routine
- Measure pH and EC at the same time each day, for example in the morning. Write it down and trends appear.
- Check water and air temperature. In a hot climate the main problem is warm water; a tank in afternoon sun can pass 30°C.
- Top up evaporated water, then measure EC again, since topping up dilutes the nutrient.
- Look at roots and leaves. Healthy roots are white or cream; brown roots with a smell are a warning.
Every 2–3 weeks, replace the whole tank and rinse the growing channels.
Mistakes beginners often make
- Never mix A and B concentrates together. Pour each into the tank water separately, or minerals bind and settle out and the plants go short.
- Adjust a little, then wait 15–30 minutes before measuring again. Big additions make values swing.
- Calibrate your meters. An uncalibrated pH pen can be far off.
- Water and electricity sit close together. Run pumps and appliances through a residual-current breaker.
When you are ready to automate
Once hand care makes sense, add temperature and light sensors, send readings to your phone, and alert when a value leaves its range. At Baan Rak Phak the system measures every 10 seconds and only alerts on things that need action; see the article on the edge + cloud smart farm for details.
Sources
The ranges in this guide are values commonly used for hydroponic lettuce, adjusted from the author's own growing. Watch your own plants and adapt to your conditions.