Hydroponic Growing Media — Canada
Rockwool, LECA, coco coir, perlite, oasis — the five media every Canadian hydroponic grower meets. How each behaves, which suits DWC vs Kratky vs drip, and what's worth buying at the hydro shop vs Canadian Tire.
Short version: Rockwool for seedlings (everyone). LECA clay pebbles for net-pot filling in DWC and Kratky. Coco coir for drip systems and Dutch bucket tomatoes. Perlite as a mix-in for drainage. Oasis foam for fast seedling starts in commercial-style NFT. Most Canadian home growers run just two: rockwool to start seeds, LECA to support them in net pots. Buy hydroponic-grade rockwool and coco; perlite and LECA can come from anywhere.
Hydroponic media don't feed plants the way soil does — their job is anchoring roots and holding moisture/air at the right ratio. Pick the wrong medium for your system and the plant either drowns or dries out. This page walks through the five most-used media in Canadian hydroponics, what each one does well, and the matchups to systems and crops.
The Five Media at a Glance
| Medium | Best for | Reusable? | Cost (CAD) |
|---|---|---|---|
| Rockwool cubes | Seedling starts, all systems | No (one cycle) | $8/24-cube tray |
| LECA clay pebbles | Net pot filler (DWC, Kratky), semi-hydro houseplants | Yes (indefinite) | $20–35 / 50L |
| Coco coir | Drip systems, Dutch bucket tomato/pepper, seed starts | Partial (1–3 yrs) | $12–20 / brick |
| Perlite | Drainage additive, ebb-and-flow | Yes (rinse first) | $15 / 50L |
| Oasis foam cubes | Fast seedling starts, NFT | No (one cycle) | $15/100-cube |
The Five Media in Detail
🪨 Rockwool
Spun mineral wool, very high water-holding capacity, sterile, inert. Cube format (2.5 cm) is the universal seedling starter for hydroponics. Soak in pH 5.5 water for an hour before use to drop manufacturing residue. Wear gloves with dry cubes — the fibres irritate skin.
Use it for: Starting every hydroponic seedling. Drop the rooted cube straight into any system once true leaves appear. Avoid in drip systems with infrequent watering — it can stay too wet.
🍅 LECA (clay pebbles, Hydroton)
Fired-clay pellets, porous, hard, lightweight. Doesn't break down. Drains beautifully. The standard net-pot filler for DWC and Kratky. Also the entire medium for the semi-hydroponics ("semi-hydro") houseplant movement — clay pebbles in a clear pot with a nutrient reservoir at the bottom.
Use it for: Surrounding rooted seedlings in net pots; entire growing medium in semi-hydro houseplants; topping mixed-media buckets to suppress algae. Rinse and reuse indefinitely. LECA for houseplants guide →
🍉 Coco coir
Shredded coconut husk. Renewable, soil-like to handle, high water-holding capacity. Buy hydroponic-grade ("low-EC" or "washed") coco bricks — cheap garden-grade coco carries sodium that disrupts nutrient balance. Expand a brick in water; one brick fills a 9-litre pot.
Use it for: Drip systems and Dutch bucket tomatoes/peppers, where its moisture retention shines; seed starting if you don't want rockwool. Often used 70% coco / 30% perlite for better drainage.
❄️ Perlite
Puffed volcanic glass. Lightweight, drains fast, provides air space. The classic drainage additive for any potting or hydroponic mix. Floats — not a great solo medium for net pots. Wear a dust mask when handling dry; wet first or soak the bag.
Use it for: Mixing into coco at 30%; topping the surface of mixed-media buckets; drainage layer at the bottom of large pots. Cheapest hydro medium per litre at any Canadian garden centre.
🪡 Oasis foam cubes
Florist's foam-style green cubes engineered for fast seedling rooting in NFT. Faster germination than rockwool, slightly cleaner to handle. More expensive per cube and not as forgiving of irregular watering. Industry-standard for commercial NFT lettuce production.
Use it for: Production-style NFT setups. Skip for hobby Kratky or DWC — rockwool is cheaper and works as well.
Which Medium for Which System
| System | Seedling start | Net pot / container fill |
|---|---|---|
| Kratky | Rockwool cube | LECA around cube in net pot |
| DWC | Rockwool cube | LECA around cube in net pot |
| NFT | Rockwool or oasis cube | No additional medium; cube sits in channel |
| Drip / Dutch bucket | Rockwool cube | Coco coir + 30% perlite, or LECA |
| Ebb & flow | Rockwool cube | LECA (drains fast between floods) |
| Semi-hydro houseplants | Existing plant (transitioned) | LECA only |
Where to Buy in Canada
- Hydro shops (Brampton Wholesale, Indoor Garden, etc.): Best for rockwool, hydroponic-grade coco, oasis cubes. Bulk LECA also competitive.
- Amazon.ca: Reliable for rockwool, LECA, oasis cubes, perlite, coco bricks. Smaller bags fine for hobby use.
- Canadian Tire / Home Depot / Rona: Perlite is identical to hydro-shop perlite at a fraction of the price. Bonsai sections sometimes carry clay pebbles cheaper than LECA. Avoid garden-centre coco unless labelled "low EC" or "washed."
- Local garden centres: Variable. Always check the label for hydroponic-grade designation.
Frequently Asked Questions
Can I reuse rockwool cubes?
Not really — rockwool used cubes are too tangled with old roots to start a new seedling cleanly and may carry pathogens. They're cheap enough at $8/24 cubes to use one cycle and toss. Compost them outdoors as a soil amendment.
How do I clean LECA between crops?
Pick out old root material, rinse thoroughly in a colander, then soak overnight in dilute hydrogen peroxide solution (3% peroxide diluted 1:10 with water). Rinse again and dry. Sterilised LECA is ready for another cycle. Done right, the same LECA serves for years.
Why does my coco coir lock up calcium?
Untreated coco coir naturally binds calcium and magnesium ions, leaving plants short of both even with proper nutrient dosing. Quality hydroponic-grade coco is pre-buffered with calcium chloride to load those binding sites before you use it. Cheap garden-centre coco is rarely buffered — expect deficiency unless you supplement Cal-Mag heavily for the first few weeks. Buy buffered coco or expect to buffer it yourself.
Is hydroton/LECA the same as akadama for bonsai?
No — both are fired clay but akadama is a much finer particle (1–6 mm) intended for bonsai soil mixes, and it breaks down faster. Hydroton/LECA is larger (8–15 mm) and engineered for indefinite reuse in hydroponics. You can use small LECA for bonsai but akadama for hydroponics will clog and degrade quickly.