One of the most important parts of running a healthy hydroponic system is getting your nutrient schedule right. In soil-based gardening, nutrients are slowly released over time. But hydroponics relies on a consistent supply of fertiliser to keep your plants thriving. And that makes figuring out how often you should you be adding fertiliser to your hydroponics system tricky. The better you understand on your system, your plants, and how you monitor nutrient levels, the easier it is to stay on top of your feeding schedule—without overdoing it.
And if after reading this guide you’re still unsure, come visit us at our Melbourne shop or give us a call on (03) 9555 6667 for expert advice.
Why Fertiliser Frequency Matters
In hydroponics, plants don’t have access to stored nutrients in the soil. Everything they need has to come directly from the nutrient solution. If the nutrient levels drop too low, growth slows or stops. If they’re too high, you risk nutrient burn, pH issues, or even root damage.
Which is why you have to top up or replace your nutrient solution at the right time. Regular monitoring helps, but keeping ahead of problems by having a general schedule is better.
Daily Monitoring, Weekly Adjustments
A good rule of (a green) thumb for most systems is to check your nutrient solution daily and adjust weekly. Monitoring your EC (electrical conductivity) and pH levels lets you know when plants are taking up nutrients or if anything’s off balance. This gives you a more accurate picture than just following a rigid calendar.
Check EC and pH Daily
Your EC tells you how concentrated your nutrient solution is. pH affects how easily your plants can absorb nutrients. By checking both each day, you can catch problems early and keep your system balanced.
Top Up with Plain Water
As water evaporates or is taken up by plants, the nutrient concentration in your reservoir increases. Topping up with plain water helps maintain the right balance without pushing EC levels too high.
Adjust Nutrient Levels Weekly
Once a week, reassess your EC and pH. If the nutrient strength has dropped, you can add more fertiliser to restore it. Some growers also do a full solution change weekly for peace of mind.
Our Product Recommendation
MILLS Basis A/B Set
A professional two-part nutrient formula designed to support plants through both vegetative and flowering stages, promoting robust root zones and vigorous growth.
Special Note
Always add Basis A to water and mix thoroughly before adding Basis B. Do not premix the two concentrates together, as this can cause nutrient lockout.
Full Nutrient Changes vs Top-Ups
If you’re running a large system with stable EC and pH readings, you might get away with topping up and rebalancing for a couple of weeks before a full flush. On the other hand, smaller systems or faster-growing plants might benefit from weekly changes to prevent nutrient imbalances or salt build-up.
There is no easy answer here. There are too many variables, so you need to learn what works best for your system, plants, and environment.
Fast-Growing Plants
Leafy greens like lettuce and herbs grow quickly and often need fresh nutrients more frequently to support steady development.
Flowering or Fruiting Plants
During bloom stages, plants have higher nutrient demands. They may need mid-week top-ups on top of your weekly schedule to keep up with growth and production.
Our Product Recommendation
MILLS C4
An advanced bloom stimulator formulated to enhance flower development, increase yield, and improve overall plant health during the flowering phase.
Special Note
Use C4 from week 2 of the flowering stage for best results.
Recirculating Systems
These systems reuse water, which means salts and unused nutrients can accumulate. A full flush every 1–2 weeks helps prevent nutrient lockout and keeps things running smoothly. But test rather than guess.
Non-Recirculating or Drip Systems
In these systems, nutrients don’t recirculate, so top-ups are usually enough. However, occasional full changes still help maintain long-term balance.
What About Automatic Dosing?
If you’re using an automatic dosing system, you can be more flexible with frequency. These systems monitor EC and pH in real-time and make micro-adjustments throughout the day. That means you can maintain a consistent nutrient level with fewer full changes, although periodic flushing is still recommended to prevent salt build-up in the reservoir.
Our Product Recommendation
HY-GEN Humiboosta
A liquid humic acid supplement that improves nutrient uptake and enhances plant vigour, suitable for all hydroponic substrates and growing mediums.
Special Note
Regularly flush your system to prevent nutrient and plant waste buildup when using this product.
Check Your Sensor Calibration
Even with automation, it’s important to manually check your sensor calibration regularly. Incorrect readings can throw off your dosing and affect plant health.
Tailor Your Schedule to Your Crop
Different plants have different nutritional needs at various growth stages. A seedling doesn’t need the same level of nutrients as a plant in full bloom, so your fertiliser frequency (and concentration) should evolve as your crop grows.
Seedling Stage
At this stage, plants are sensitive. Use a diluted nutrient mix and top up only as needed. Full changes are usually not necessary unless EC drifts.
Vegetative Stage
Growth speeds up here, and so do nutrient demands. Increase both the strength and frequency of your feeds. Weekly nutrient changes and mid-week top-ups are common.
Flowering Stage
Flowering and fruiting demand high nutrient uptake. Weekly full changes with more frequent top-ups help avoid deficiencies and maintain productivity.
Always refer to the specific nutrient schedule and dilution for the fertiliser you’re using. Dumping and reloading nutrients weekly is not going to lead to overfeeding your crop. But using more than the recommended nutrient dilution can.
Final Tips for Getting It Right
Keep a Log
Tracking your EC, pH, temperature, and fertiliser adjustments gives you a clearer picture of what’s working. It also makes it easier to troubleshoot if something goes wrong. But keep a record of everything, don’t rely on memory alone in the beginning.
Flush Periodically
Even with top-ups, it’s smart to completely flush your system every few weeks to clear out built-up salts and restore balance. If you’re testing regularly and keeping a record, you’ll eventually have a better idea of how often to do this with your setup and types of plants.
Start Small
If you’re unsure about frequency or strength, take a cautious approach. It’s easier to increase nutrients than to deal with overfeeding.
Our Product Recommendation
CYCO Ryzofuel
A premium root stimulant that promotes rapid root development and overall plant health, ensuring a strong foundation for successful hydroponic growth.
Special Note
Ryzofuel is designed for use with indoor/outdoor plants, seedlings, bulbs, and trees.
There’s no one-size-fits-all answer to fertiliser frequency in hydroponics but staying consistent with your monitoring and being responsive to what your plants need will give you the best results. Whether you’re growing herbs on a benchtop or managing a larger set-up, a steady hand on nutrient management keeps everything healthy and productive.
For expert advice and premium nutrients made for Aussie growers, check out the full range at A-Grade Hydroponics. We’ve got everything you need to dial in your grow.
