No, your floating plants do not need injected CO2 to grow well. The whole point of floating plants CO2 access is that their leaves sit on top of the water in open air. They pull carbon dioxide straight from the atmosphere, so they never depend on the small amount dissolved in your tank. This is great news if you run a low-tech planted tank and want fast green growth without buying any gas gear. You can keep your setup simple and still watch them spread across the surface.
Look at how a floater is built and the answer makes sense to you. Plants like duckweed, frogbit, and water lettuce keep their main leaves above the surface. Those leaves breathe the air the same way a houseplant on your windowsill does. The roots dangle below to drink up nutrients, but the green parts that handle photosynthesis stay dry and exposed. Your floater is really half air plant and half water plant, and that split is its big advantage.
Submerged plants face a much harder problem than yours do. They live underwater, so they can only use the carbon dioxide dissolved in the liquid around them. Water holds far less of this gas than air does. Many plants in a busy tank fight over that limited supply, and growth slows when it runs short. This is why a high-tech carbon dioxide aquarium often runs an injection system to feed hungry stem plants and dense carpets.
Your floaters skip that whole fight. Air holds a steady, basically endless amount of carbon dioxide, and floating leaves tap right into it. That direct line to the air is the main reason these plants grow so fast for you. A healthy frogbit can double its leaf count in a week or two with no special gear at all. Duckweed moves even quicker and can blanket a quiet surface in days.
Aquascapers lean on this trick every day, and you can too. Floaters are a go-to algae fix in tanks that run no injection, since they grow quick enough to starve algae of light and nutrients. They soak up extra nitrate from your water and shade the layer below, which keeps green slime from taking hold. That makes them one of the easiest tools for a quiet, gear-free setup. Many keepers add a handful of frogbit right when a new tank starts to fight that early algae bloom, and it works because no gas tank is needed.
Give your floating plants strong light from above and keep their leaves dry. These two things matter far more than any gas you could inject.
So here is the practical move for you. Skip the CO2 gear for your floaters and put that money toward a good light instead. The floating plants CO2 supply is already free in the air, so spending on gas adds no real growth. Bright, steady light from above is what drives their fast growth, and it costs less than an injection rig over time. A simple full-spectrum light over the tank does the job and keeps your running costs low for years.
Keeping the leaves dry matters just as much for you. Water droplets and condensation under a tight lid can rot floating leaves and slow them down. Leave a small air gap above the surface so the tops can breathe. Aim any filter flow so it does not push your plants under or splash them all day. A gentle surface and a calm corner help them spread fast. You can pen them into one area with a floating ring or a length of airline tubing if you want a tidy mat. Do those two things and your floaters will thrive while pulling free carbon dioxide right out of the air.
Read the full article: Floating Plants: Benefits, Care and Risks
