Feeding hydroponic plants correctly is one of the most important skills you'll develop as a grower — and one of the most common areas where beginners go wrong. Unlike soil, which holds a reserve of organic nutrients that break down slowly over time, hydroponic and coco coir systems rely entirely on you to deliver the right nutrients, at the right concentration, at the right frequency. Get it right and plants grow fast, stay healthy, and produce strong yields. Get it wrong and problems can compound quickly — deficiencies, toxicities, root damage, and stunted growth can all stem from a feeding programme that's slightly off-track.
💧 Why Feeding Consistency Matters in Hydroponics
Plants require a continuous supply of macro and micronutrients to fuel photosynthesis, cell division, and fruit or flower production. In a hydroponic system, the nutrient solution is the plant's only food source — there's no soil biology to buffer shortfalls or break down organic matter over time. This means consistency in your feeding routine is critical.
A general principle that holds true across most crops: feeding volume and nutrient concentration should increase as the plant grows. A small seedling in week one needs a fraction of what a large vegetating plant in week six requires. Scaling your feed alongside plant development keeps growth balanced and prevents the two most common beginner mistakes — chronic underfeeding from fear of overfeeding, or overloading a small root zone with a full-strength solution too early.
If you're unsure where to start, visit a reputable hydroponics shop. Bring the details of your system, your growing medium, and the crop you're growing — a knowledgeable team member can walk you through a feeding programme suited to your specific setup.
📋 How to Read a Hydroponic Nutrient Feeding Chart
Nutrient feeding charts are provided by manufacturers (such as Canna, Athena, House & Garden, or Plagron) and can look complex at first glance. The key is to break them down week by week rather than trying to interpret the whole chart at once.
Week numbers mean daily feeds, not weekly feeds
This is the most common misreading of feeding charts. Week 1 does not mean one feed per week — it means the dosage listed for Week 1 should be applied every day throughout that seven-day period. Each subsequent week typically adjusts the dose of one or more nutrients slightly to match the plant's changing nutritional demands as it moves through vegetative growth and into flowering.
EC and PPM: measure what you mix
Feeding charts give you a starting point, but the most reliable way to know what your plant is actually receiving is to measure the electrical conductivity (EC) of your nutrient solution using a calibrated EC meter. EC measures the total dissolved mineral content of your solution — a higher reading means more nutrients, a lower reading means fewer. As a general guide:
- Seedlings and early propagation: 0.8 – 1.2 EC
- Vegetative growth: 1.4 – 2.0 EC
- Flowering and fruiting: 1.8 – 2.4 EC
- Late flower / flush: Plain water or very low EC (0.4 – 0.6)
These are indicative ranges. Always cross-reference with your specific nutrient brand's feeding chart, as formulation strength varies between products. Your water's baseline EC (before adding nutrients) also affects the final reading — subtract this from your mixed solution EC to get an accurate picture of nutrient load.
💡 A-Grade Tip: Always pH your nutrient solution after mixing all nutrients together — not before. The target pH range for most hydroponic and coco grows is 5.8 – 6.2. Outside this range, certain nutrients become unavailable to the plant even if they're present in the solution, leading to deficiency symptoms that look like underfeeding but aren't.
🌱 Underfeeding vs Overfeeding: What Actually Happens
The fear of overfeeding is widespread among new growers — and it leads many of them to underfeed instead, which is often the more damaging outcome. Understanding what both look like helps you make confident adjustments.
Signs of underfeeding
- Pale or yellowing leaves, starting from older (lower) growth
- Slow growth rate despite adequate light and temperature
- Thin stems and small leaf development
- EC of runoff noticeably lower than your feed solution (plant consuming all available nutrients)
Signs of overfeeding (nutrient toxicity or salt build-up)
- Dark green, clawing, or burnt leaf tips — often called "nutrient burn"
- Crispy or brown leaf margins
- EC of runoff significantly higher than your feed solution (salt accumulation in the medium)
- Slowed growth despite heavy feeding — a sign of osmotic stress at the root zone
Monitoring runoff EC is one of the most useful tools for catching feeding problems early. If your runoff EC is climbing significantly above your feed EC, flush with plain pH-adjusted water to reset salt levels before resuming your normal programme.
💡 A-Grade Tip: Don't chase individual deficiency symptoms with single-element correctors until you've ruled out pH as the cause. A pH that's drifted outside the 5.8 – 6.2 range locks out specific nutrients and mimics deficiency symptoms exactly. Fix pH first, then reassess.
⚙️ Feeding in Coco Coir: Key Differences
Coco coir and coco-perlite blends are the most popular growing media in Australian hydroponics — and they behave differently from soil or rockwool in ways that directly affect how you should feed.
Coco is an active, water-loving medium
Unlike soil, coco coir has a very high water-holding capacity but also excellent drainage and aeration. It's a fundamentally different substrate to grow in — dry roots in coco equals stressed or dying roots. Coco should never be allowed to dry out completely between feeds. For established plants, feeding to slight moisture at all times — with a target of around 5% runoff per feed — keeps the root zone healthy and prevents salt accumulation.
Feeding frequency in coco
Seedlings in small pots may need one to two feeds per day depending on temperature and light intensity. Larger plants in their final containers during peak vegetative or flowering growth may require multiple feeds daily. The goal is to maintain consistent moisture and nutrient availability without waterlogging the medium.
A useful indicator: if your plants are draining their pots completely dry within a single day, it's time to transplant into a larger container. A root zone that's too small for the plant's demand cannot hold adequate nutrient solution between feeds, which limits uptake and restricts growth.
Cuttings vs seedlings in week one
Feeding charts don't always distinguish between cuttings and seedlings in the early weeks — but the difference matters. A rooted cutting arrives with an established root system and can absorb a greater volume of solution than a germinated seedling of the same age. Start cuttings at the lower end of the week one EC range and scale up quickly as the root zone develops. Seedlings should be treated more conservatively — start with a very mild solution (0.8 – 1.0 EC) and increase only once you see healthy new leaf growth.
Getting Your Feeding Programme on Track
Hydroponic feeding is a skill that develops with observation. Feeding charts are a reliable starting framework, but reading your plants — growth rate, leaf colour, stem strength, and runoff EC — is what takes your results to the next level. Trust the chart, measure your EC and pH consistently, and adjust based on what you observe rather than reacting to every minor change.
If you're unsure about any aspect of your feeding programme, the A-Grade team is here to help. Call us on (03) 9555 6667, email grow@agradehydroponics.com, or come into our hydroponics store at 60/148 Chesterville Road, Cheltenham. We're happy to walk through your setup and get you on the right track.
