Floating Plants for Aquariums

Floating plants are some of the simplest plants to grow. They sit at the surface, close to the light, with access to carbon dioxide from the air, so they tend to grow quickly even in tanks without injected CO2. That speed is both their main benefit and the main thing you need to manage.

Are floating plants good for a planted tank?

• Nutrient uptake. Fast-growing floaters draw nitrate, phosphate, and other nutrients from the water column. Removing a portion regularly takes those nutrients out of the tank, which can leave less for algae.
• Shade. A partial layer of leaves softens bright light. This suits fish and plants that prefer dimmer conditions, and can reduce algae in tanks where the light is stronger than the plants can use.
• Cover. Trailing roots give small fish, fry, and shrimp somewhere to hide and graze. Surface-dwelling fish often use the roots for shelter.
• Easy indicator plants. Because floaters grow quickly, changes in their color or growth can be an early sign that nutrients are running low.

Which floating plants are best for aquariums?

Availability varies by region, and some species are restricted in some places. Check local rules before buying.

Salvinia

Several small Salvinia species are kept in aquariums. Their hairy, water-repellent leaves sit on the surface and multiply quickly. Be careful with identification. Giant salvinia, Salvinia molesta, is listed as a Federal Noxious Weed in the United States, which the USDA National Invasive Species Information Center notes makes it illegal to import or move between states without a permit. Buy from a reputable source and confirm the species.

Amazon frogbit

Amazon frogbit, now often classified as Hydrocharis laevigata, forms rosettes of floating leaves with spongy undersides and long roots. Its Wikipedia entry notes that the leaves need to stay dry to avoid rotting, so it does poorly under heavy condensation or splashing. It has also escaped into waterways in California and other regions after use in aquariums and ponds, which is a good reminder of why disposal matters.

Red root floater

Tropica describes Phyllanthus fluitans as having small, round, water-repellent leaves that range from light green to deep red depending on lighting, with roots that are often red. Tropica adds that it does well with little surface movement and can grow quickly and soon block light from the plants underneath.

Duckweed

Duckweed grows very fast and absorbs nutrients well, but it is notoriously difficult to remove once it is in a tank. Tiny fronds cling to nets, hands, and equipment and spread to other tanks. Many keepers deliberately avoid it, and new plants are sometimes checked for hitchhiking duckweed before going in.

Water lettuce

Water lettuce forms large rosettes with long, feathery roots, and generally only suits large tanks with open tops and plenty of space above the water. The USDA National Invasive Species Information Center lists it as an invasive aquatic plant that grows into dense mats that clog waterways. It may be restricted where you live, so check local rules before acquiring it.

Do floating plants block light from other plants?

A full mat of floating plants can cut most of the light reaching the substrate. Light-hungry plants such as carpets and red stem plants are usually the first to suffer, growing leggy or losing color. Shade-tolerant plants such as Anubias, Java fern, and cryptocorynes cope better.

To keep a balance:

• Cover only part of the surface, often leaving open areas over plants that need more light.
• Thin floaters regularly, removing a portion at each water change.
• Watch plants below for signs of low light, such as stretched stems and wide gaps between leaves.

Aquarium light intensity and duration explains how light levels affect growth, and the lighting hub covers fixtures.

How do you keep floating plants in one spot?

Floating plants drift wherever the current takes them, often piling up against the filter outflow or blocking the light. A simple barrier keeps them in one area.

• Floating rings or corrals. Many keepers use a ring of airline tubing joined into a loop, or a section held in place with suction cups, to hold floaters in one zone.
• Away from the outflow. Strong surface currents push floaters underwater, where leaves get wet and may rot.
• Away from intakes. Loose fronds and roots can clog filter intakes.

Surface agitation and the CO2 trade-off

Floaters prefer calm water, but surface movement drives gas exchange. Agitation brings oxygen in and lets carbon dioxide out. A thick mat of floaters on a still surface can reduce oxygen exchange, especially at night when plants and animals both consume oxygen.

In tanks with injected CO2, there is a trade-off. Calmer surfaces hold more CO2, but too little movement can leave fish short of oxygen. Keep some open, gently moving water even when you grow floaters. If fish gather at the surface or breathe rapidly, increase agitation and thin the floaters. The aquarium CO2 system guide and the planted aquarium filter guide cover flow and gas exchange.

Common mistakes

• Letting floaters cover the whole surface. Plants below lose light and may decline.
• Adding duckweed casually. It is hard to remove once established.
• Placing floaters under strong flow. Wet, submerged leaves tend to rot.
• Heavy condensation under a tight lid. Water dripping onto leaves can damage species such as frogbit.
• Forgetting gas exchange. A dense mat on still water can leave fish short of oxygen.
• Throwing excess plants outside. Dispose of them in sealed bags in the trash, or give them away.
• Not checking local rules. Some species are restricted where you live.

Next steps

• Balance light for floaters and the plants below with aquarium light intensity and duration.
• Use floaters as part of your algae strategy with planted tank algae troubleshooting.
• Pair them with shade-tolerant plants from easy aquarium plants for beginners.
• Provide cover for shrimp with shrimp in planted tanks.
• Match plants and equipment to your tank with the setup finder.