The short answer
Dose liquid carbon once a day, following the rate printed on your bottle for your tank’s water volume. Every brand is concentrated differently, so the bottle — not a generic online figure — is your reference. Start at the lower end, dose consistently, and watch how your plants and animals respond before increasing.
How to dose it properly
- Measure by actual water volume, not tank size on the box — subtract substrate and hardscape.
- Dose daily, ideally near the start of the light period when plants are photosynthesising.
- Start low. Try half the recommended dose for the first week, then work up to the full rate if all looks healthy.
- Dosing straight into the flow (near a filter outlet) helps it disperse.
Liquid carbon is a limited supplement, not a miracle. It provides an easier-to-use carbon source than dissolved CO2, which can nudge growth and, at the recommended dose, help knock back some algae. It will not turn a low-light tank into a high-tech carpet machine.
Plants and animals that dislike it
Some plants react badly even at normal doses:
- Vallisneria, some mosses, Anacharis (Elodea) and certain stem plants can melt or stall.
- Shrimp and sensitive fish can be stressed by overdosing — respect the limits.
If you keep any of these, test with a reduced dose first and stop if you see melting.
When to use it — and when not to
Liquid carbon suits low- to medium-light planted tanks where you want a small boost without a CO2 cylinder. If you’re chasing demanding plants or a dense carpet, you’ll get far better results from pressurised gas — see CO2 for beginners and our best CO2 system picks.
For feeding the rest of what plants need, pair it with a balanced fertiliser from our fertiliser hub, and see what nutrients aquarium plants need.