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Liquid carbon aquarium fertiliser

Updated: October 2026

You add a bottle every day and want carbon without a gas kit. Liquid carbon aquarium fertiliser, in this set, means AquaDesign CARBO 2,500 ml. It leaves nitrate, phosphate, iron, and potassium to a nutrient bottle. The [aquatic plant fertiliser comparison](/hub/fertiliser-soil-and-bark-mulch/aquatic-plant-fertiliser) includes that listing beside the feeds. The Products Compared editorial team read the amazon.co.uk page as stored on 19 October 2026: about £19.99, 4.6 from 71 reviews. This is not a laboratory test of algae or of livestock. If you buy through our links, we may earn a commission at no extra cost to you. Buy CARBO when the gap is carbon, keep a nutrient bottle, and stay at or under the daily maximum.

You add a bottle every day and want carbon without a gas kit. Liquid carbon aquarium fertiliser, in this set, means AquaDesign CARBO 2,500 ml. It leaves nitrate, phosphate, iron, and potassium to a nutrient bottle.

Our top picks

Easy Life Easy-Life ProFito 500 ml

Best overall

Easy Life Easy-Life ProFito 500 ml
8.6/10about £9.49
View offer
AquaDesign AquaDesign CARBO 2,500 ml

Alternative

AquaDesign AquaDesign CARBO 2,500 ml
7.0/10about £19.99
View offer
AquaDesign AquaDesign PLANT+ 500 ml

Alternative

AquaDesign AquaDesign PLANT+ 500 ml
7.3/10about £10.99
View offer
On this page
  1. 1.What this bottle is
  2. 2.How much the listing allows
  3. 3.Algae, without a promise
  4. 4.Who should skip it

What this bottle is

CARBO sits on the carbon corner of the planted-tank triangle. Practical Fishkeeping says liquid carbon is less efficient than injected CO2. The listing says a daily dose increases plants' uptake of fertiliser, which assumes a fertiliser is already there. Reviewers often buy CARBO beside a weekly nutrient bottle. That pairing matches the listing better than using CARBO alone. The active ingredient is not named, so this page does not invent one. The maker's 1,000 ml page repeats the daily rates and mentions 1 pump per 60 litres. This listing is 2,500 ml with a 3 ml pipette, and the model field says carb5L. Seachem Flourish Excel is a different product. The nutrient bottle is chosen on the buying guide.

How much the listing allows

The amazon listing says 1 ml per 50 litres a day, and a maximum of 2 ml per 50 litres a day. A 100 litre tank is 2 ml a day, or 4 ml at the maximum. The pipette is 3 ml, so that standard dose is under one pipette. The pump-per-60-litres line belongs to the other size. That daily figure is a carbon schedule, not a template for ProFito, PLANT+, PLANT LITE, or Flourish. Putting the carbon figure on a nutrient bottle, or dosing PLANT+ every day at the carbon rate, mixes the two jobs. Practical Fishkeeping is plain that an overdose of liquid carbon is toxic. The listed maximum is the stop, including on a day the plants pearled. Iron and potassium still sit on the other bottles.
Easy Life Easy-Life ProFito 500 ml

Testsieger

Easy Life Easy-Life ProFito 500 ml
8.6/10about £9.49
View offer

Algae, without a promise

One bullet says CARBO kills unwanted algae. That is the listing claim, not a result from a UK trial in this file. Of 12 UK reviews read, one keeper reported black hair algae clearing from leaves and bogwood across three years. Another bought it for that claim and saw no difference after three months. Practical Fishkeeping describes pressure on some algae, including painting black beard algae, as a side effect of liquid carbon in general. A product sold to kill algae can fall under HSE biocidal rules, and this pass did not retrieve an authorisation number for CARBO. Buy it as carbon, at the daily rate, and judge algae as an uncertain extra.

Who should skip it

Skip CARBO if it would be your only bottle. Plants still need the minerals that ProFito, PLANT LITE, PLANT+, or Flourish are sold to supply, depending on the nitrate test. Skip it if you will not measure a daily millilitre. Skip it as a shrimp product. The listing does not say it is safe for shrimp or fish. One reviewer reported no effect on Amano shrimp. That is one tank, not a safety trial, and the ingredient is unstated. For a small tank that will not justify a gas kit, CARBO at 1 ml per 50 litres a day is the carbon option in this set, used with a nutrient bottle and stopped at 2 ml per 50 litres.

Common questions

Is liquid carbon the same as plant fertiliser?
CARBO is sold under a fertiliser title and it supplies carbon on a daily schedule. ProFito and PLANT+ supply nutrients on a weekly schedule, and ProFito states that nitrate and phosphate are not included. You can run CARBO beside one of those. Using CARBO as the only bottle leaves the mineral side uncovered. Practical Fishkeeping treats injected CO2 as the more efficient carbon source when you want faster growth.
How much CARBO per day for 50 litres?
The listing says 1 ml per 50 litres a day, and 2 ml per 50 litres a day as the maximum. The kept bottle includes a 3 ml pipette, so the standard 50 litre dose is one third of a pipette. The maker's 1,000 ml page prints the same millilitre rates. A pump rate on that other size is not the instruction for this 2,500 ml pipette bottle.
Can I replace injected CO2 with it?
Practical Fishkeeping says liquid carbon is less efficient than gas, so growth is slower, and that the liquid habit can cost less in a small tank. CARBO can be the carbon you add when you are not running a gas kit. It does not match a pressurised CO2 setup for speed of growth. Stay at or under 2 ml per 50 litres a day, because overdose is the documented risk for this class of product.
Does it kill black beard algae?
The listing says it kills unwanted algae. One of 12 UK reviews reported black hair algae clearing over three years. Another reported no change after three months. Practical Fishkeeping mentions a side effect on some algae, including painting black beard algae, for liquid carbon in general. Those sources do not add up to a promise that this bottle will clear black beard algae in your tank.
Is it safe for shrimp and fish?
This listing does not make a shrimp or fish claim. One reviewer saw no effect on Amano shrimp. That single comment is not a safety test. EasyCarbo's overdose warning in a UK gear review applies to a different brand and is a reminder that liquid carbon past the maximum can harm livestock. Dose the 1 ml rate, and stop at the 2 ml maximum.
Should I still buy ProFito or PLANT+?
Yes, if the plants need nutrients as well as carbon. ProFito fits a stocked, moderate tank that should not receive extra nitrate. PLANT+ is the all-in-one weekly dose when a fast, high-light tank tests short of nitrate. CARBO's own bullets talk about helping plants take up fertiliser, which assumes the fertiliser is a separate bottle.

Related pages

How to dose aquarium fertiliser

Best aquarium plant fertiliser

Aquatic plant fertiliser

Aquarium plant fertiliser buying guide: pick a type

Complete vs lite aquarium fertiliser for your tank

Sources

Public UK and maker sources from the research digest, used for this page in October 2026. Prices, stars and review counts are from the nine amazon.co.uk listings captured on 19 October 2026. A shrimp-safe bullet is a listing claim. Flourish's copper figure is the maker's statement, not an independent UK lab test. CARBO's algae line is not confirmed here as an HSE authorisation.

  1. Practical Fishkeeping, growing aquarium plants (retrieved 19 October 2026)
  2. Practical Fishkeeping, gas versus liquid carbon (retrieved 19 October 2026)
  3. Seachem Flourish (retrieved 19 October 2026)
  4. Seachem Flourish dosing instructions (retrieved 19 October 2026)
  5. Easy-Life ProFito (retrieved 19 October 2026)
  6. GOV.UK, manufacturing and marketing fertilisers (retrieved 19 October 2026)
  7. GOV.UK, product labelling (retrieved 19 October 2026)
  8. HSE, regulated biocides (retrieved 19 October 2026)