This hydroponics FAQ answers the questions Australian growers ask us most at the A-Grade Hydroponics store in Cheltenham, Melbourne. Most indoor growing problems trace back to a handful of variables: pH, EC, nutrient solution temperature, light and air. Get these right and plants grow fast and clean; let one drift and you'll see yellow leaves, burnt tips or root rot.
💧 Hydroponics FAQ: Nutrients, pH & EC
What pH should I maintain in a hydroponic system?
Keep your nutrient solution between pH 5.5 and 6.5. Most nutrients are highly available within this range, and it applies to recirculating systems and coco coir alike. We recommend aiming for 5.8–6.2 to leave a buffer either side.
pH drifts as plants feed, so check it daily and correct with pH Up or pH Down in small doses.
What EC should I run?
EC (electrical conductivity) measures the total dissolved salts in your solution, which tells you how strong the feed is. Seedlings and cuttings need a weak solution, and EC rises as plants grow. For fruiting crops, Ohio State University's hydroponic tomato fact sheet gives roughly 2.0–2.4 mS/cm. Targets vary by crop, so start with your nutrient's feed chart.
Do I really need pH and EC meters?
Yes. Checking pH and EC daily, at the same time of day, alerts you to any problems early. Without pH testers and EC testers, you can't tell whether a yellowing leaf is a pH, strength or deficiency problem.
💡 A-Grade Tip: Calibrate your meters with fresh calibration solution and store your pH probe in storage solution, never plain or distilled water. A poorly stored probe drifts and gives false readings.
What water is best for hydroponics?
Low-salt water gives you the most control over your feed. Melbourne is well placed: Melbourne Water's published testing shows electrical conductivity of roughly roughly 40–190 µS/cm (0.04–0.19 mS/cm) at its major storages. Other regions can be much harder, so test your supply.
RO (reverse osmosis) water needs calcium and magnesium added back with CalMag. For chlorine or chloramine, a water conditioner designed to neutralise it is an option.
Why are my leaf tips burning?
The most common cause is an overly strong nutrient solution. As plants drink and water evaporates, salts concentrate and EC climbs. Check EC, then dilute with fresh pH-adjusted water or flush. Some deficiencies can also cause tip burn.
A note on buying nutrients in Australia: according to the APVMA, fertilisers fall under state and territory regulations rather than APVMA registration, but products based on plant hormones must be registered.
Why are my leaves turning yellow?
Yellowing (chlorosis) usually points to a nutrient uptake problem. Common causes include:
- pH outside the 5.5–6.5 range, locking out nutrients
- A genuine deficiency, such as nitrogen
- Nutrient solution that's too hot or too cold
- Salt build-up in a solution that hasn't been changed
- Grow lights hung too close to the canopy
Check pH and EC first to rule out the most likely causes.
🌡️ Reservoir Temperature, Aeration & Root Rot
What temperature should my nutrient solution be?
The most widely recommend root zone temperature is 20–24°C. Warmer water holds less dissolved oxygen, and high temperatures favour Pythium root rot. In a Melbourne summer that can mean a water chiller; in winter, a water heater stops the solution dropping too low overnight.
💡 A-Grade Tip: On a heatwave day with no chiller, freeze a few sealed 2L bottles of water and float one in the reservoir. Swap them as they thaw, and never add ice directly to your nutrient solution.
Should I aerate the nutrient solution?
Yes, for almost every system. The same Cornell guidance recommends keeping dissolved oxygen above 6 mg/L (ppm), ideally close to saturation at 8–9 mg/L. Air pumps and air stones are the simplest way to get there. The exception is the Kratky method, which relies on an air gap above the solution instead of active aeration.
What causes plants to die suddenly?
After ruling out the obvious, check the roots. Healthy roots are white to cream; brown, slimy, foul-smelling roots indicate root rot, most often caused by Pythium. Warm, poorly oxygenated solution is the main trigger.
Fungus gnats often get the blame, but research has found adult gnats do not transmit Pythium. They're attracted to plants that are already diseased. Larvae have spread Pythium under laboratory conditions, so controlling fungus gnats is always recommended - but fix temperature and oxygen first.
💡 Grow Lights & Photoperiod
How long should I run my grow lights?
For leafy, vegetative growth, 18 hours on and 6 hours off is a common indoor schedule. Whether you then switch to 12/12 depends on the plant. Short-day plants bloom when days are shorter than about 12 hours, while day-neutral crops such as tomatoes, cucumbers and corn flower regardless of day length.
For short-day plants, the dark period must be completely dark. Light leaks interrupt the night and can stop flowering, so seal your tent and use a reliable timer.
How do I measure my grow light's output?
Use a quantum (PAR) meter. It measures PPFD, the light reaching your canopy in µmol/m²/s. Multiply PPFD by hours of light and 0.0036 to get DLI (daily light integral) in mol/m²/day. For example, 500 µmol/m²/s for 18 hours gives a DLI of 32.4.
Should I use LED or T5 grow lights?
T5 fluorescents suit seedlings, cuttings and propagation but lack the output for mature plants. Full-spectrum LED grow lights now cover the whole cycle, from vegetative growth through flowering, and are generally more energy efficient than HPS. Choose fixtures tested to Australian electrical standards.
⚙️ Grow Room Environment
What humidity should I maintain?
As a working guide, we recommend around 60–65% relative humidity in vegetative growth and 50–55% in flowering. Prolonged high humidity invites grey mould (Botrytis), which spreads quickly in small tents. Mount a hygrometer inside the room, keep reservoirs covered to cut evaporation, and extract moist air with fans.
How much ventilation do I need?
Fan size depends on room volume, the heat your lights produce and outside conditions. Start with volume: a 1.2 x 1.2 x 2m tent holds 2.88m³ of air. Our fan requirements calculator turns that into an extraction rate. Size up slightly and use a speed controller rather than undersizing.
What size reservoir should I use?
Larger reservoirs keep pH, EC and temperature more stable. Our rule of thumb is at least 50L for a 1.2 x 1.2m grow space and 100L for a 1.2 x 2.4m space.
🌱 Hydroponics FAQ: The Key Takeaways
Most hydroponic problems come back to the same fundamentals: pH between 5.5 and 6.5, EC matched to the crop and growth stage, a cool and well-oxygenated reservoir, the right photoperiod and steady airflow. Measure these regularly and you'll catch problems before your plants show them.
Still stuck? Bring a photo and your pH and EC readings into our Cheltenham store, call us on (03) 9555 6667, or browse our water control range online. Better data makes for better harvests.
