Houseplants in the Aquarium: Growing Pothos and Co. with Roots in the Water
A pothos with its roots hanging into the aquarium and its vines growing over the rim: it doesn't just look great, it also does something useful for your tank. Houseplants with their roots in the water take up nutrients from the aquarium and compete with algae. Here I show you which plants are suitable, how to set them up and what to keep in mind.
Why houseplants in the aquarium?
Plants that grow with their roots in the water and their leaves in the air are called emersed. They have a big advantage over aquatic plants: they get CO2 from the air and plenty of light from above. That is why they often grow vigorously and take up nitrate and phosphate from the water along the way.
- Fewer nutrients for algae. Whatever the plant takes up is no longer available to algae.
- Hiding spot under water. The root network is a popular refuge for shrimp and fry.
- Looks. The tank looks bigger and more alive because the green grows beyond the water surface.
Which plants are suitable?
Robust houseplants that tolerate hydroculture and root easily from cuttings work well:
- Pothos: the classic, extremely robust and fast growing.
- Philodendron: just as easy, with beautiful heart-shaped leaves.
- Monstera cuttings: need a bit more space, but look spectacular.
- Syngonium: compact and available in many leaf colours.
- Tradescantia: grows very fast and is a great nutrient consumer.
Important: only the roots belong in the water. Leaves and stems that stay under water permanently will start to rot.
How to set up the plant
1. Cutting instead of potted plant. The easiest way is to start with a cutting. Cut a stem just below a node, the spot where a leaf or an aerial root grows. That is where the water roots will form later.
2. No soil in the tank. If you take a rooted plant out of its pot, rinse the roots very thoroughly. Potting soil and fertiliser have no place in an aquarium.
3. Put it in the basket. Place the cutting in the plant basket so that the node sits just in the water. If it doesn't stand steady on its own, a few lava stones or some expanded clay in the basket help.
4. Be patient. After one to three weeks the first water roots appear. After that it usually goes fast.
The plant basket
To keep the plant secure with only the roots reaching into the water, I designed a hanging plant basket. It hangs on the rim of the tank and is height adjustable. That way it fits different tank rims and you can readjust it when the water level changes.
It comes in three sizes:
| Size | Dimensions | Good for |
|---|---|---|
| S | 5 x 6 x 8 cm | a single cutting, also for small tanks |
| M | 10 x 6 x 8 cm | two to three cuttings |
| L | 15 x 7 x 8 cm | several plants or a small group |
Light and care
The plants need light for their leaves. Usually the aquarium lighting together with normal room light is enough. If the tank is very dark, the plants grow more slowly but rarely die.
You normally don't need extra fertiliser, the plants get their nutrients from the aquarium water. If the roots get very long over time, you can simply trim them. Remove dead root parts so they don't rot in the tank.
Good to know
- The plant basket is made for freshwater aquariums.
- Many houseplants like pothos are toxic to pets such as cats if they nibble on them. So hang the basket where curious housemates can't reach it.
- If you also have floating plants in the tank, the plants compete for nutrients. That is good against algae, but can slow down the growth of each individual plant.
Quick summary
- Pothos, philodendron, monstera, syngonium and tradescantia work well.
- Start with a cutting and keep soil out of the tank.
- Only the roots go in the water, the leaves stay outside.
- A hanging plant basket keeps everything securely in place.
More ideas against algae and excess nutrients can be found in the article How to control duckweed in your aquarium. Questions? Feel free to write to me via the contact page.