- Tap the Reservoirs tab to add your first grow system — name it, set the volume, and you're set.
- Your reservoir appears on the Home screen. Tap the green Log + button to record a reading instantly — no menu digging.
- Use the Mix tab to calculate nutrient doses for any bottle size and reservoir volume.
- Toggle between US (gallons / °F) and Metric (litres / °C) using the US/M button at the top-right — all values update everywhere, instantly.
- Set your source water's baseline EC in Settings for accurate readings across all calculators.
Why is my home screen blank after creating a reservoir?
Pull down to refresh, or navigate away and back to the Home tab. If the issue persists, close and reopen the app. Reservoirs appear automatically once saved.
How do I log a metrics reading from the home screen?
Tap the green Log + button on your reservoir card, then choose Add Metrics Reading. Enter your EC, pH, temperature, and water volume, then tap Save.
How do I add photos to my Grow Journal?
Open your reservoir → Grow Journal → tap + → in the Photo section, tap Choose from Library or Take Photo. Camera and library access require granting permission when prompted — this only happens once.
How do I export my journal as a PDF?
Open your reservoir's Grow Journal. Once at least one entry exists, an export icon appears in the top toolbar. Tap it to share the full PDF via AirDrop, email, or any other app.
What should my EC target be?
General guidelines: Seedlings 0.8–1.2 mS/cm · Vegetative 1.2–2.0 mS/cm · Flowering 1.8–2.4 mS/cm. Always consult your specific nutrient brand's feed chart, and set your source water baseline EC in Settings for accurate readings.
How do I change my default nutrient line?
Go to Settings (last tab) → tap Default Nutrient Line → choose from the list. The Concentrate Mixer will open to this line by default.
My data disappeared after updating the app. What happened?
All data is stored locally on your device and is fully preserved through app updates. If data appears missing, verify you're on the same device and haven't reset app data via iOS Settings → HydroponicsCalc. Contact us immediately if you've experienced data loss.
Does the app require an internet connection?
No. HydroponicsCalc is 100% offline. All calculations run on your device. No account, no sign-in, and no internet connection is ever required.
Does HydroponicsCalc work on iPad?
Yes — HydroponicsCalc is a universal app built for both iPhone and iPad. On iPad, the interface adapts to the larger screen with an optimised multi-column layout.
Can I use the app in metric units?
Yes. Tap the US/M button in the top-right corner of the app to switch globally between US (gallons / °F) and Metric (litres / °C). All calculators and logs update instantly.
Concentrate Mixer
Use "Bottle → EC" for normal mixing, or "Target EC → Dose" to work backwards from a desired nutrient strength.
EC Calculator
Set your source water's baseline EC in Settings. The calculator subtracts it automatically so you know what your roots are actually getting.
pH Calculator
Use Calibration mode to tune the titration ratio if your real-world pH adjustments differ from the estimates — this happens with different product concentrations.
VPD Calculator
The leaf temperature offset accounts for the fact that leaf surfaces run cooler than ambient air. A starting point of −3°F (−1.7°C) works well for most setups.
Top-Off Calculator
After evaporation, your reservoir EC rises because only water evaporates — nutrients stay. The Top-Off calculator tells you exactly how much plain water and concentrate to add.
Harvest ROI
Track nutrient cost per gram by logging your spend. Add your light wattage and electricity rate in Settings to include energy costs in your cost-per-gram calculation.
Still stuck?
Send us an email and we'll get back to you within one business day. No bots — a real person reads every message.
support@hackerhomelab.comTypical response time: less than 24 hours on business days