A beautifully planted aquarium is one of the most stunning things in the hobby, but plants can be frustratingly difficult to grow if you don't understand the three things they need: light, CO2, and nutrients. Get these three in balance and plants grow vigorously. Get them out of balance and you'll have algae and dying plants.
The Three Pillars of Plant Growth
Think of plant growth as a triangle. Light drives photosynthesis. CO2 is the carbon source plants use to build tissue. Nutrients (nitrogen, phosphorus, potassium, and trace elements) are the building blocks. Increase one without the others and you cause problems, most commonly algae.
Light: How Much Is Enough?
- Low light: java fern, anubias, java moss, cryptocorynes. No CO2 injection needed.
- Medium light: most stem plants, vallisneria, amazon swords. CO2 beneficial but optional.
- High light: carpet plants (HC cuba, dwarf hairgrass, monte carlo). CO2 injection required.
Run your lights 6–8 hours per day maximum. More than 8 hours causes algae, not faster plant growth. A timer is essential. If you're fighting algae, reduce your photoperiod to 5–6 hours first.
💡 The most common planted tank mistake is running cheap, low-output lights for 10+ hours per day to compensate. This causes algae without giving plants what they need.
CO2: Do You Need It?
CO2 injection is not mandatory for a planted tank, but it dramatically accelerates plant growth and outcompetes algae. At low to medium light levels, plants can survive on CO2 dissolved naturally in water. At high light levels, CO2 injection is essential.
CO2 injection systems
A basic CO2 setup consists of: a pressurised bottle, regulator, check valve, diffuser, and drop checker. Target 30ppm CO2 in the water column, indicated by a drop checker turning yellow-green.
Budget CO2 options
DIY yeast CO2 generators are cheap but inconsistent. Small disposable cartridge systems (Fluval CO2, JBL ProFlora) are a good middle ground for tanks up to 60L.
Nutrients: What Plants Actually Need
Macronutrients
Nitrogen (N), phosphorus (P), and potassium (K) are the primary macronutrients. In a fish tank, nitrogen and phosphorus are usually present from fish waste. Potassium often needs supplementing. Use a liquid fertiliser containing all three.
Micronutrients
Iron and other trace elements are essential for healthy colouration, particularly in red plants. Iron deficiency causes yellowing of new leaves while old leaves stay green. Supplement with a comprehensive trace element fertiliser.
Root tabs
Heavy root-feeding plants (amazon swords, cryptocorynes, vallisneria) benefit enormously from root tabs, slow-release nutrient capsules pushed into the substrate near roots. Add new tabs every 3 months.
Beginner Plants That Rarely Fail
- Java fern: grows in any light, attach to rock or wood, never bury the rhizome
- Anubias: extremely hardy, grows in low light, attach to rock or wood
- Java moss: grows anywhere, great for shrimp tanks and breeding setups
- Cryptocoryne wendtii: may melt when first planted but recovers strongly
- Vallisneria: fast growing, excellent natural filtration
- Hornwort: almost unkillable, excellent for absorbing nitrates
Why Your Plants Are Melting
New plants often melt when first introduced. This is normal; they're transitioning from nursery (emerged) growth to submerged growth. Don't remove them. Leave the roots and rhizome in place. Within 2–4 weeks, new submerged leaves will emerge and the plant will recover.
If established plants start melting, check CO2 levels, light duration, and whether any nutrients are deficient. Yellow old leaves = nitrogen deficiency. Yellow new leaves = iron or micronutrient deficiency.
Find CO2 systems, LED grow lights, liquid fertilisers, and root tabs in our Planted Tank range.
