Aquarium

API CO2 Booster Liquid Carbon for Freshwater Plants — 16 oz Brown

4.8 12 reviews 2 min read Updated 11 October 2026

Star rating

4.8/ 5

Customer reviews

Published on this page

5 stars 10
4 stars 1
3 stars 1
2 stars 0
1 star 0

Brand

API

Product description

Includes: one (1) 16‑ounce bottle of API CO2 Booster freshwater plant treatment in a brown plastic bottle.

Formulation and purpose: This product is a concentrated liquid carbon supplement made to give aquatic plants the carbon they need for photosynthesis in a form they can absorb from the water column. The formula supplies carbon both as dissolved CO2 and as simple organic carbon compounds that plants can take up through their leaves.

How it works: The treatment gradually releases usable carbon into the aquarium water so plants can assimilate it without relying solely on gaseous CO2 injection. It is intended to be applied regularly — typically daily — following the directions on the label to maintain a steady supply of carbon for growing plants.

Compatibility and safety: The booster is compatible with freshwater fish and will not alter aquarium pH when used as instructed. It can be applied on its own or in combination with a pressurized CO2 system to supplement carbon levels. For fuller fertilization coverage, use it alongside leaf and root fertilizers (for example, complementary leaf-zone and root-tab products from the same manufacturer).

Use and storage: Shake before use and follow label dosing for tank size and stocking. The brown bottle helps protect the concentrate from light; store in a cool, dry place and keep out of reach of children. With regular application, plants typically show improved vigor and coloration while some types of algae may be reduced.

Pros

Provides both dissolved CO2 and simple organic carbon
Easy liquid dosing for daily use
Formulated not to alter aquarium pH

Cons

Some invertebrates (snails) may be sensitive
Not a complete fertilizer on its own
Requires consistent daily application for best results

VerdictThis 16 oz liquid carbon supplement provides readily available carbon for aquarium plants by delivering a mix of dissolved CO2 and simple organic carbon compounds. It’s easy to dose daily, won’t upset aquarium pH, and pairs well with root tabs and leaf fertilizers for comprehensive plant care. Generally safe for fish and many shrimp, though some invertebrates like snails may be sensitive. Useful f

Customer reviews

kaleb 5/5

Controls hair algae, shrimp are fine with it

Helped weaken hair algae in a tank near a sunny window and the shrimp have been happily grazing on the remains. Will keep a bottle on hand to tackle outbreaks.
Cindy 5/5

Helps plants but affected my snails

My plants exploded after I started using this and I’d recommend it for growth. I did notice my snails reacted poorly, though. Overall still effective for the vegetation.
Mamagalof4 4/5

Beginner-friendly and effective

Very simple to use for newcomers. Worked especially well on pearlweed in my tank.
Planted Junkies 5/5

Exceeded my expectations

Very satisfied with the results; my plants responded quickly and the product was reliable.
Suzy S. 5/5

Noticeable acceleration in growth

I strongly recommend this—my plants started growing rapidly over the course of about a month. Photos show the change clearly.
Mariah Nelson 5/5

Unexpectedly good for algae control

I bought this to help my plants but it didn’t change them much; instead it helped control algae. I use it across five tanks and the bottle lasts a long time since doses are small. Safe around my shrimp and fish.
Kindle Customer 5/5

Daily dosing produced great results

Used daily in my planted freshwater tank and the plants are producing offshoots; fish are doing well. One delivery arrived cold and the plastic cracked when dropped, but I salvaged the liquid into another bottle. I buy it regularly; the smaller bottle fits neatly on my shelf.
William D-S 5/5

Keeps plants green and is simple to use

Does what it claims — keeps plants fresh and green with no negative effect on my fish. Recommend buying the larger size if you have a bigger aquarium.
G K Sukumar 5/5

Plants thriving, fish unharmed

Arrived well packed and I’ve used it in two small tanks with fast plant growth and no observable harm to the fish. Works well alongside a general starter kit to keep systems balanced.
Muraki TTM 5/5

Revived dying moss — curious results

I compared this with another CO2 tablet product and tracked levels with a drop checker. After treating, my yellowed moss began to recover and produce new growth. Hard to say if it’s true gaseous CO2, but it clearly supplied useful carbon.
Jude 5/5

Good boost for new setups

Handy for jump-starting plant growth in new aquariums and helping established tanks recover.
Arifin Satej 3/5

Label language mismatch

The online description suggested English instructions, but my bottle only had Chinese labeling. It would have been helpful to include an English insert or directions.