What house plants can I put in a fish tank?

The one rule: roots in, leaves out

Every plant in this guide is a land plant. Its leaves are built for air, and its crown (where stems and roots meet) expects to stay dry. Put just the roots in water and many houseplants adapt well, growing new water roots that are thinner and whiter than their soil roots. Push the leaves and crown under, and the plant rots, usually over a few weeks to a few months.

So the pothos vines you see tumbling out of tanks online are sitting above the water with only their roots dangling in. That is the whole trick. The rest is choosing a plant that copes, preparing it so it does not poison the tank, and managing the roots.

8 house plants that work with roots in tank water

These are the plants fishkeepers most often grow this way with success. None is a true aquatic plant, so results vary with room light, temperature and how the plant was started.

Pothos (Epipremnum aureum)

The default choice for good reason. Pothos roots readily from a cutting with at least one node (the bump where a leaf joins the stem), tolerates low room light, and keeps growing for years with its roots in water.

Heartleaf philodendron (Philodendron hederaceum)

Looks and behaves much like pothos, with softer, heart-shaped leaves. Cuttings root easily in water. Treat it exactly as you would pothos.

Monstera cuttings (Monstera deliciosa)

A cutting with a node and an aerial root will root in water and can grow on that way for a long time. It gets big and heavy, so support it from a wall, shelf or stake rather than the tank rim.

Peace lily (Spathiphyllum)

Copes well with bare roots in water, which is why it turns up in vase-and-betta kits. Keep the crown and leaves above the waterline.

Syngonium (Syngonium podophyllum)

Also called arrowhead plant. Cuttings root quickly in water and grow well with leaves in the air.

Lucky bamboo (Dracaena sanderiana)

Already sold standing in water, so it adapts easily. The lower stems can sit in the water, but keep the leafy tops well clear. It is not a bamboo, and like other dracaenas it rots if kept fully submerged.

Spider plant (Chlorophytum comosum)

The plantlets on the runners root in water within a week or two. Spider plant is one of the few common choices generally listed as non-toxic to cats and dogs, which helps if you have a curious cat.

Herb cuttings: mint and basil

Mint roots in water almost immediately and grows vigorously. Basil roots too, though it is short-lived and tends to flower and fade within a season. Watercress (Nasturtium officinale), a genuine stream-edge plant, prefers cooler water and suits an unheated tank better than a tropical one. Never eat anything harvested from a tank that has had medication or other treatments added.

Plants to avoid, including "aquarium plants" that are really houseplants

This is the part most guides skip. Plenty of plants sold in fish shops as aquarium plants are terrestrial or bog plants grown out of water on a nursery bench. Submerged, they can look fine for weeks or months while they burn through stored energy, then turn soft and collapse. The usual suspects:

• Mondo grass (Ophiopogon japonicus), often sold as "dwarf grass".
• Purple waffle or red ivy (Strobilanthes alternata, formerly Hemigraphis).
• Aluminium plant (Pilea cadierei).
• Caladium, sold for its coloured leaves.
• Dracaena varieties, including lucky bamboo, when planted fully underwater.
• Peace lily and syngonium sold submerged, sometimes as "Brazilian sword" and "arrowhead". Fine with leaves in air, slow death underwater.

A rotting plant adds waste to your ammonia load and feeds algae. If you have bought one, lift it out and grow it with its leaves in the air instead. For plants that genuinely grow underwater, see our aquarium plants guide.

Also be wary of fresh garden-centre and supermarket plants. Ornamentals are sometimes treated with systemic insecticides, which are taken up into the plant tissue and cannot be rinsed off, and shrimp and other invertebrates are far more sensitive to insecticides than fish. And never put any tank plant, cutting or root trimming into a pond, stream or drain: bin or compost it.

Are they toxic? What the evidence actually says

Pothos, philodendron, monstera, peace lily and syngonium all contain calcium oxalate crystals. If a pet or child chews the leaves, the crystals cause pain, drooling and swelling in the mouth. Pet poison references list them as toxic to cats and dogs, and lucky bamboo appears on those lists too. Think about where the leaves hang.

For fish, the honest answer is that there is very little formal research either way. The crystals sit inside the plant's cells, and the known harm comes from chewing, not from roots sitting in water. What does exist is plenty of hobbyist experience of pothos and peace lily kept over tanks for years without obvious problems. That is reassuring but not proof, so keep fish known to shred plants (goldfish and larger cichlids, for example) away from the roots, and remove any roots that turn brown and mushy.

Preparing a plant before it goes on the tank

None of this guarantees a plant is free of systemic pesticide, but new growth on a cutting you rooted yourself is about as low risk as it gets. With shrimp, start with one small cutting and watch them for a couple of weeks before adding more.

How to mount house plants on a fish tank

• Hang-on planters. Small baskets or cups that hook over the rim, holding the crown above water while the roots trail down. The tidiest option.
• The hang-on-back filter. Tuck a cutting into the media chamber of a HOB filter so the roots sit in flowing water. Do not remove so much media that you lose biological filtration, and keep roots clear of the flow path and impeller.
• Near the filter outflow. A small basket by a canister return gets good water movement and keeps roots away from the intake.
• Wedging in lid gaps. Free and simple, but every gap is an escape route. Avoid it with jumpers such as hatchetfish, killifish and bettas unless the gap is sealed around the stem.

Keep leaves off hot light units, and support heavy plants so the tank rim is not taking the weight.

What they do for water quality, and what they don't

Plants with roots in the water take up nitrogen as they grow, including nitrate, the end product of the nitrogen cycle. With their leaves in open air and plenty of carbon dioxide, vigorous growers like pothos can outpace many submerged plants, and faster growth means more uptake.

How much that matters depends on how much plant you have and how heavily stocked the tank is. A couple of small cuttings over a busy tank will barely register on a test kit. A large, established pothos over a lightly stocked tank can make a noticeable difference over time. For the bigger levers, see how to lower nitrate.

Light, roots and ongoing care

Light

The leaves use room light, not the tank light. Bright indirect light suits most of these plants, and pothos and peace lily tolerate fairly dim rooms. You do not need to change your aquarium lighting, and fish waste supplies the nutrients, so never dose houseplant feed into the water. If you are tempted, read about fertiliser in fish tanks first.

Managing the roots

In a mature tank, roots can grow long and thick quickly. Trim them with clean scissors when they dominate the view, reach the substrate or drift towards the filter intake, where they can cause a blockage. Shrimp and small fish often graze the film on the roots, and fry use them as cover. Pull out any roots that go brown and soft.

Water loss

Plants draw water up through their roots and release it from their leaves, so a large plant adds noticeably to evaporation. Top up with dechlorinated water more often, especially with a HOB filter that needs the water level high to run.

Common mistakes

• Burying the crown. If the base of the stems sits underwater, expect rot.
• Treating a vase as a home. A peace lily on a bowl does not filter or heat the water. Bettas need a proper filtered, heated tank; see our betta care guide.
• Expecting it to fix overstocking. Plants help at the margin; too many fish or too much food still needs fixing at the source.
• Forgetting the cat. Trailing leaves at cat height are an invitation to chew.