Why Aquarium Plants Float and How to Anchor Them
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If my aquarium plants keep floating, the cause is usually simple: the plant is not anchored yet, it was planted too shallowly, or it is a type that is meant to float. Rooted plants stay down once their roots hold the substrate, and until then they need to be pushed in properly and kept in place. This guide explains why plants rise, which plants are supposed to float, and how to plant each type so it stays where you put it.
Quick answer
- Plants float when nothing holds them down: loose roots, leftover foam or weights removed badly, or planting too shallow.
- Push each plantlet root-first into the substrate with tweezers, about 5 cm deep for most bunch and potted plants, then press the substrate back around the base.
- Do not bury the whole plant or push a bulb deep; both cause problems.
- Some plants are sold as floating plants on purpose. They sit on the surface and do not need anchoring.
Why aquatic plants float in the first place
Many water plants are built to stay upright in water without stiff, woody stems. According to the Wikipedia article on aquatic plants, fully submerged plants need little stiff tissue, and gas-filled spaces or lightweight packing cells (aerenchyma) help keep them upright in the water. That same lightness is why a freshly planted stem can lift out of the gravel: the plant has buoyancy, and it has no roots established yet to hold it.
The same article separates plants by how they live in the water. Submerged plants may be rooted in the substrate or unrooted. Floating-leaved plants are rooted but let their leaves rest at the surface. Free-floating plants have no anchorage to the substrate at all. So when a plant rises, the first question is which of these groups it belongs to. A free-floating plant at the surface is behaving normally. A rooted plant at the surface means the planting did not hold.
Check the plant type before you fix anything
A guide from Swell UK lists six common ways aquarium plants are sold, and each is planted differently:
- Bunch plants, for example Cabomba, Hygrophila, Egeria, Elodea and Vallisneria.
- Potted plants, for example Echinodorus bleherae and Cryptocoryne.
- Bare-root plants.
- Tissue-cultured plants, for example Lilaeopsis and Hemianthus.
- Bulb plants, for example Aponogeton and Nymphaea.
- Floating plants, which go on the water surface with the leaves facing up.
Identify yours from the label or the way it came packed. A bulb plant that is buried will behave very differently from a bunch plant that was left with its weight on.
How to anchor each type
Bunch plants
Bunch plants usually arrive held together by a foam strip and a metal weight. The Swell UK guide says to remove and discard both, then separate the plantlets. Leaving the foam and weight on can cause the plantlets to rot. Trim the roots to about 1 cm, then use fine tweezers to push each plantlet root-first about 5 cm into the substrate. When you plant several in a group, space them about 5 cm apart. The guide also warns against using large, clumsy tweezers, because they enlarge the planting hole and can pull the plant back out as you withdraw them.
Potted plants
Slide the plant out of its pot and take off any ceramic weight. Strip away as much rockwool as you can, trim the roots, and rinse if needed. Push each plantlet root-first to about 5 cm, then press the substrate back around the base. Modern Aquarium gives a very similar method: remove the plant from the pot, separate the roots from the rockwool, trim the plant to fit your substrate, rinse the roots, and divide it into smaller bundles before planting.
Bare-root plants
Trim any roots and plant individual plantlets the same way you would potted plants.
Tissue-cultured plants
These come in a gel. Rinse the gel off and separate the plantlets, or cut matted carpeting plants into chunks and plant them as a group. Use a fine substrate and do not bury the plant too deeply. The Swell UK guide lists burying most of the plant as a common mistake.
Bulb plants
Place the bulb on top of the substrate and its roots will grow down by themselves. The guide quotes that pushing the whole bulb deep into the substrate is not advised, because bulbs need oxygen around them. If a bulb plant keeps floating, check that it was not pushed in so far that it is rotting, and that it is simply resting on top.
Floating plants
Set them on the water surface with the leaves facing up. The guide notes that strong flow can turn leaves over, so check that the leaves are upright after you place them. Modern Aquarium adds that floating plants are designed to float along the top of the aquarium without any access to the substrate, and that brackets or a corral can control where they sit.
Substrate matters for holding roots
Modern Aquarium recommends a nutrient-rich substrate with small grains so plants anchor well, and a layer about 2 to 3 inches deep so roots can take hold. For rooted plants, its steps are to dig holes in the substrate deep enough to fully cover the roots, then heap the substrate back around the plant without covering the foliage. If your layer is very thin, a plant has little to grip. If the grains are very coarse, small roots may not hold. The Swell UK guide also advises a fine substrate for tissue-cultured plants.
Another point from Swell UK: when you plant, push the plant root-first and do not drag the tweezers sideways. Pulling sideways opens the hole and the plant pops back up as soon as you let go.
Other things that can lift a plant
The sources above explain planting technique, but they do not give a full list of everything that can pull a plant loose. What they do show is that strong flow can turn floating leaves over and that a bigger hole from clumsy tools can let a plant slip back out. If a plant rises soon after you plant it, check three things in order: whether the roots are fully covered, whether any foam strip or weight was left on, and whether the plant is a type that was never meant to be buried.
For tied-in plants, the Wikipedia article on aquascaping mentions that plants can be positioned by tying them in place inconspicuously with thread. That is the only attachment method that page describes, and it does not explain how to attach moss or similar plants to rock or wood, so this guide does not either.
Plants that suit a small betta tank
If the tank is a small betta setup, you can choose plants that need less fuss. Modern Aquarium describes Anubias as hardy, low in light needs, and tolerant of 69 to 86 degrees F, and notes that plants in one tank should have similar temperature, nutrient, lighting and substrate needs. Whatever you choose, match the plant to the tank and plant it properly. For more ideas on betta-friendly greenery, see our guide to aquarium plants for a betta tank, and if your issue is with surface plants specifically, read about floating plants for betta fish.
Step-by-step checklist
- Work out which type of plant you have: bunch, potted, bare-root, tissue-cultured, bulb or floating.
- Remove packaging that should not go into the tank: foam strips, metal or ceramic weights, rockwool and gel.
- Separate the plantlets and trim the roots as needed (about 1 cm for bunch plants).
- Use fine tweezers to push each plantlet root-first about 5 cm into the substrate.
- Press the substrate back around the base and make sure the leaves are not buried.
- For bulbs, rest them on the substrate. For floating plants, place them on the surface leaf-side up.
- Check again after a short time and replant any that have lifted.
Common mistakes
- Leaving the foam strip and metal weight on bunch plants, which can cause the plantlets to rot.
- Using large tweezers that widen the planting hole.
- Pushing bulbs deep into the substrate.
- Burying tissue-cultured plants so that most of the plant is covered.
- Planting a substrate layer too thin to hold roots.
FAQ
Why do my new aquarium plants float after I plant them?
Submerged plants are built to be light in water, and a new plant has not grown roots into the substrate yet. If the roots are not covered, or the plant was pushed in only a little way, it can rise. Replant it root-first about 5 cm deep and press the substrate around the base.
Should I remove the metal weight from bunch plants?
The Swell UK guide says to remove and discard the foam strip and metal weight, then separate the plantlets, because leaving them on can cause rot.
Do all aquarium plants need to be planted in the substrate?
No. Floating plants sit on the surface and have no need of the substrate, and bulb plants are placed on top of it rather than buried.
How deep should a substrate layer be?
Modern Aquarium suggests a 2 to 3 inch layer so roots can take hold, using small-grained, nutrient-rich substrate.
Can I just tie a plant down?
The aquascaping article on Wikipedia mentions tying plants in place with thread. It does not describe other attachment methods, so check what the plant label says for your specific species.
What if my plant is a floating type that keeps drifting?
Modern Aquarium notes that brackets or a corral can control where floating plants sit at the surface.
Bottom line
Identify the plant type first, then plant it the way that type needs: strip packaging, trim roots, push root-first into fine substrate about 5 cm deep, and leave floating and bulb plants alone on the surface or top of the substrate. A plant that is planted right and has time to root stops rising.
