Aquarium plants without CO2

Nearly every plant here lists CO2 as not needed, a stronger claim than beneficial. A plant marked none grows at full health on the carbon a stocked tank makes on its own. That works because most plants here list low or medium light, and strong light without carbon grows algae instead. Floaters such as the red root floater and floating ludwigia list high light and take their CO2 from the air. The Senegal tea plant, water starwort and red mangrove also list high light. Liquid carbon is optional, and a few plants here react badly to it. The waterweed, sold as anacharis, reacts worst, and a large dose can melt vallisneria leaves. Hobbyists report hornwort melting under it too. Fish and food supply the rest, and a root tab under the crypts and vals covers what they take from the substrate.

1. 01

   None means none

   Not merely beneficial: full growth without it

2. 02

   Mostly low or medium light

   Strong light without carbon grows algae

3. 03

   The tank makes the carbon

   Fish, food and mulm supply enough

4. 04

   Liquid carbon is optional

   Waterweed and vallisneria react badly to it

The Canadian waterweed is marked beginner for low light, a stem that grows to 23.6 inches (60 cm) and roots wherever it lands. The hygrophila polysperma is the same rating at 17.7 inches (45 cm). The Brazilian pennywort grows fast to 19.7 inches (50 cm) with round leaves on a creeping stem. The creeping Charlie is 15.7 inches (40 cm) of the same habit. The moneywort is a slow, upright stem with round leaves at 11.8 inches (30 cm), marked beginner. The ambulia is a feathery stem marked easy for low light at 15.7 inches (40 cm). The hygrophila polysperma and ambulia are US federal noxious weeds. Neither can be shipped or carried across state lines without a USDA permit. Some states, such as Florida, also list both as noxious weeds.

The anubias barteri is the standard large form at 13.8 inches (35 cm), marked beginner. The anubias petite is a small form at 2 inches (5 cm), marked easy. The Windelov java fern has lace-cut leaf tips, the trident java fern forked ones, and both are marked beginner with the plain fern's care. The java moss is marked beginner and grows on anything. The willow moss is a cool-water moss, marked easy at 4.7 inches (12 cm). All of them are tied to wood or rock with the rhizome in the water, never buried.

The cryptocoryne wendtii red is marked beginner for low light, the red plant for a tank without CO2 at 5.9 inches (15 cm). The cryptocoryne spiralis is a tall crypt at 13.8 inches (35 cm). The giant vallisneria reaches 59.1 inches (150 cm) and lies along the surface in a normal tank; the dwarf vallisneria stays at 15.7 inches (40 cm). The Echinodorus palifolius is a sword marked easy with no CO2. Its underwater rosette stands 11.8 to 15.7 inches (30 to 40 cm) tall. It sends aerial leaves up toward 39.4 inches (100 cm), so it suits an open-topped tank. The Crinum calamistratum is a bulb with crinkled leaves to 39.4 inches (100 cm), marked easy for low light. All of them want a root tab.

Floating plants take their carbon from the air, so none of the floaters here needs CO2. The dwarf water lettuce is marked beginner, a rosette at 3.9 inches (10 cm) with hanging roots. The salvinia natans is a floating fern marked beginner that doubles every couple of weeks. The red root floater turns red under strong light at the surface. The water spangles is Salvinia minima, a small salvinia marked easy. The duckweed is marked beginner and impossible to remove once it is in. The floating water sprite is a loose surface fern marked easy, 15.7 inches (40 cm) tall and 9.8 inches (25 cm) across.