Oxygenating Plants Guide: Weighted, Free-Floating and Potted Oxygenators

Why oxygenating plants matter

Oxygenating plants are one of the most useful groups of pond plants. They help make a pond feel more alive, more natural and better balanced.

They are especially valuable in new ponds, wildlife ponds and ponds that feel underplanted. They add living plant growth, create underwater and pond-edge cover, and help build the natural structure of the pond.

They are also often misunderstood. Oxygenators are sometimes described as if they are a quick cure for green water. That is not quite right. They are not an instant algae treatment, and they do not work in isolation. Their real value is that they help create the conditions for a healthier, clearer and more stable pond over time.

The best results usually come when oxygenators are used generously and as part of a balanced planting scheme. That means combining them with surface shade from water lilies or floating plants, edge structure from marginal plants, and sensible pond care.

The RHS describes pond plants as valuable because they add visual interest, encourage wildlife and can help keep water clear. It also recommends including oxygenating plants and choosing plants according to pond size, depth and style.

Read the RHS guide to pond plants.

What counts as an oxygenating pond plant?

In pond gardening, the term “oxygenating plants” is often used as a practical group rather than a single strict plant type.

Some oxygenators are classic submerged plants. These grow mainly below the water surface and provide underwater cover. Others float freely through the water. Others are rooted potted plants that grow in shallow water, around pond shelves, or at the pond edge, contributing to pond balance through their foliage, roots and overall plant growth.

It is helpful to think about three main formats:

1. Weighted oxygenator bunches
   Loose stems held together with a small weight, usually placed straight into the pond.
2. Free-floating oxygenators
   Plants such as Hornwort that float freely or semi-freely in the water.
3. Potted oxygenators
   Attractive rooted plants supplied in pots or baskets, useful for shallow water, shelves and visible pond-edge planting.

These are all useful, but they do not all work in exactly the same way.

What do oxygenating plants actually do?

Oxygenators help in several ways.

First, they add more living plant growth to the pond. As they grow, aquatic plants take up nutrients from the water and growing medium. The main nutrients involved in algae growth are nitrogen and phosphorus compounds, including nitrates and phosphates. These can enter ponds through fish waste, uneaten food, decaying leaves, decomposing plant material, runoff from fertilised ground, or nutrient-rich planting media.

Algae and blanketweed also thrive when light and nutrients are readily available. By adding more living plant growth, oxygenators help create competition for those nutrients. This does not mean they remove algae instantly, but it does mean they are part of a healthier long-term pond balance.

Second, submerged oxygenators produce oxygen during daylight through photosynthesis. That oxygen supports the wider pond ecosystem, including aquatic insects, snails, tadpoles and fish where present. Like all plants, they also respire and use some oxygen, including at night, so the benefit should not be reduced to oxygen production alone. Their wider value is in helping create a living, planted pond.

Third, they create structure. A pond with bare water and very few plants can feel empty below the surface and around the edges. Oxygenators add texture, shelter and hiding places, which are particularly valuable in wildlife ponds.

RHS wildlife pond guidance identifies underwater plants such as hornwort and water starwort as useful cover for tadpoles and other larvae.

Read the RHS guide to pond plants.

Do oxygenating plants clear green water?

Oxygenating plants can help support clearer water, but they should not be treated as an instant cure.

Green water is usually caused by microscopic algae suspended in the water. Blanketweed is the long, stringy algae that forms strands or mats around plants, baskets, pumps or pond edges.

Algae are a natural part of pond life, and a small amount is normal. The problem comes when algae grow faster than the rest of the pond can balance them.

RHS algae guidance explains that algae are particularly common in sunny ponds with little planting to shade the surface, and where nutrient levels are high. It recommends reducing nutrient levels, using low-nutrient aquatic compost when adding plants, managing fish feeding, and including enough submerged oxygenators and surface-covering plants.

Read the RHS guide to pond algae and blanketweed.

So the honest answer is: oxygenators help, but they are one part of the answer.

They work best alongside:

• water lilies or floating plants for surface shade;
• marginal plants for edge planting and habitat;
• aquatic compost rather than ordinary garden compost;
• sensible fish feeding and fish stocking where fish are present;
• removal of fallen leaves and decaying plant material;
• patience, especially in a new pond.

Barley straw can also be used as a natural support, especially preventatively in spring, but it should be treated as an aid to good pond balance rather than a substitute for planting.

Pumps, filters and UV clarifiers can also be relevant in some ponds, especially fish ponds, but they are a separate topic. They do not replace the need for good planting.

A new pond often takes time to settle. Adding oxygenators is one of the best first steps, but it is not a switch that instantly turns green water clear.

Weighted, free-floating and potted oxygenators: what is the difference?

Edenmere sells oxygenators in more than one form, and this is where many customers are unsure what to choose.

The three main formats are:

1. Weighted oxygenator bunches
2. Free-floating oxygenators
3. Potted oxygenators

All three are useful. They simply do different jobs.

Weighted bunches are loose stems of oxygenating plants held together with a small weight. They can usually be placed straight into the pond without a basket, compost or additional planting. They are the quickest and most flexible way to add oxygenating plant volume.

Free-floating oxygenators, such as Hornwort, are supplied as loose or semi-loose stems that float freely or gather naturally in the water. They are useful for open-water cover and are especially simple to add to a pond.

Potted oxygenators are rooted into aquatic pots or baskets. They are especially useful on pond shelves, in shallow areas, or anywhere you want the pond to look more deliberately planted. They give more visible structure and can be highly decorative, particularly where they produce upright stems, floating foliage or flowers.

Weighted bunches: best for speed and flexibility

Weighted oxygenator bunches are usually the easiest way to add oxygenating plants quickly.

They are a good choice if:

• your pond is new;
• the pond feels underplanted;
• you want to add oxygenators without repotting;
• you have deeper open water;
• you are creating a wildlife pond;
• you want flexible planting that can be moved or thinned later;
• you want to add plant mass quickly.

Because weighted bunches are not waiting to root through a basket before they begin growing, they are a simple way to add more submerged foliage to the pond. You place them in the water, allow them to settle, and then adjust later if needed.

Weighted bunches are also useful because they do not have to be “designed” into the pond in the same way as visible shelf planting. They can be placed in different areas to give underwater cover and help fill open water naturally.

They are not just invisible functional plants. Some oxygenators add attractive texture, surface growth or flowers. Water crowfoot, for example, can produce delicate white flowers. Starwort weighted bunches can create soft green growth at and below the surface. Milfoils add fine, feathery texture through the water. The exact look depends on the species and the conditions in your pond.

Free-floating oxygenators: simple open-water cover

Free-floating oxygenators are useful when you want an easy plant to add to open water without baskets, shelves or planting.

The main example is Hornwort. Hornwort is often used as a free-floating oxygenator. It is suitable for deeper water and can drift or gather naturally in the pond. RHS lists Hornwort as a submerged oxygenator suitable for deep water and free-floating use.

Read the RHS guide to pond plants.

Free-floating oxygenators are useful if:

• you do not have planting shelves;
• you want a very simple oxygenator option;
• you want underwater cover for wildlife;
• you have open water that feels bare;
• you do not want to plant baskets.

Because free-floating oxygenators are not fixed in place, they may move around with wind, water movement or wildlife activity. That is part of their natural behaviour. In some ponds they may group together in one area, while in others they spread more evenly.

Potted oxygenators: best for beauty, structure and shelf planting

Potted oxygenators are the better choice when you want oxygenating plants to form part of the visible design of the pond.

They are useful if:

• your pond has shelves or shallow planting zones;
• you want plants to stay in a chosen position;
• you want a more composed, planted look;
• you want upright stems, foliage, surface texture or flowers;
• you are creating an ornamental pond as well as a wildlife pond;
• you want longer-term structure rather than only quick plant volume.

Potted oxygenators can be some of the most attractive plants in a pond. They are not just functional water-balancing plants. They can bring shape, texture, foliage and seasonal interest.

Good examples include:

• Needle Spike Rush for fine, upright texture;
• Miniature Pennywort for soft, rounded surface foliage;
• Water Shamrock for decorative floating leaves;
  
• Upright Water Milfoil adds soft texture and contrast in the pond

Potted oxygenators are particularly helpful in ponds where bare shelves make the pond look unfinished. A potted oxygenator can soften that look and make the pond feel more established.

For customers who want a pond that looks beautiful as well as balanced, potted oxygenators are often the missing piece.

Weighted, free-floating or potted: which should I choose?

For many ponds, the best answer is not either/or. It is a mix.

What you need	Best choice
Fast oxygenator volume	Weighted bunches
Easiest placement	Weighted bunches or free-floating oxygenators
Deeper open-water planting	Weighted bunches or free-floating oxygenators
Flexible planting you can move or thin	Weighted bunches
Simple loose open-water cover	Free-floating oxygenators
Visible shelf planting	Potted oxygenators
More decorative structure	Potted oxygenators
A composed, planted pond	Potted oxygenators
Best all-round result	A mixture of weighted, free-floating and potted oxygenators

Choose weighted bunches if you want speed, ease and flexible underwater coverage.

Choose free-floating oxygenators if you want simple open-water cover without baskets.

Choose potted oxygenators if you want beauty, shape and more settled planting.

Choose a mix if you want the strongest overall result.

This is especially true for ponds that are new, underplanted or being improved after a period of poor balance. Weighted bunches and free-floating plants give you quick plant mass. Potted oxygenators give you structure and a more finished look.

Which gives the quickest benefit?

Weighted bunches usually give the quickest visible benefit because they add submerged plant volume straight away.

Free-floating oxygenators are also quick to add, especially where you have open water and do not want to use baskets.

Potted oxygenators contribute from the start, but they are more about settled planting and longer-term structure. As they establish, they become part of the pond’s planted design, particularly on shelves and shallow areas.

For a new pond, a practical approach is:

1. Start with weighted bunches or free-floating oxygenators to add quick oxygenator volume.
2. Add potted oxygenators to create attractive planted structure.
3. Add water lilies, marginals and floating plants where appropriate to complete the balance.

How to place or plant oxygenators

Weighted bunches, free-floating oxygenators and potted oxygenators are used differently.

Weighted oxygenator bunches

Weighted bunches usually need no compost, basket or planting.

 

Place them directly into the pond at a suitable depth and allow them to settle naturally. In still or gently moving water, the weight normally helps keep the bunch in place. Some species may remain mostly submerged, while others may produce surface growth or root into sediment over time.

You can move, thin or reposition bunches as you see how they behave in your pond.

Some customers remove the weights to let stems float freely, but this can allow the plants to gather in one place, especially where wind or water movement pushes them around. For most ponds, leaving the bunches weighted is the simplest starting point.

Free-floating oxygenators

Free-floating oxygenators are placed directly into the water and allowed to float or drift naturally.

They do not need a planting basket. They are a good choice where the pond has open water but few shelves, or where you want a simple way to add underwater plant growth.

If they gather in one area, you can gently move or thin them as needed.

Potted oxygenators

Potted oxygenators are positioned more like other planted pond baskets.

Place the pot or basket at the appropriate depth for that plant. Always check the plant label or product guidance, because different species prefer different depths and positions.

If you are potting or repotting smaller oxygenators, use aquatic compost rather than ordinary compost. Where suitable, finish the top of the basket with aquatic gravel. This helps reduce soil loss, keeps the basket tidy, looks more attractive and reduces disturbance when the basket is lowered into the pond.

Useful product links:

• Aquatic Compost
• Aquatic Gravel
• Aquatic Baskets

RHS aquatic planting guidance notes that oxygenating plants can be bought in bunches and planted into baskets, and advises anchoring them firmly. It also identifies mid-spring to early summer as the main aquatic planting period.

Read the RHS guide to pond plants.

How many oxygenating bunches and potted oxygenators do I need?

Most ponds benefit from being planted more generously than people first expect. Underplanting is one of the common reasons ponds struggle to look settled and balanced.

Use the table below as a practical Edenmere starting point for combining oxygenating bunches with potted oxygenators.

Pond size	Oxygenating bunches	Potted oxygenators
Up to 1m² container pond	5	1–2
2m² pond	10	2–3
4m² pond	15–20	3–4
6m² pond	25–30	4–5
8m² pond	32–40	5–6
10m² pond	40–50	5–7
12m² pond	50–60	5–8

Use this as a starting guide rather than a rigid rule. The right quantity depends on pond depth, sunlight, fish, existing planting, water movement and whether the pond is mainly ornamental, wildlife-focused or both.

Our recommendations are based on the way our oxygenators are supplied, the size of the bunches and baskets, and the practical planting needs of typical garden ponds.

For fuller planting guidance, see How Many Pond Plants Do I Need?.

Best oxygenator approach by pond type

Pond type	Recommended approach
New pond	Start with weighted bunches or free-floating oxygenators, then add potted oxygenators and other plant groups.
Wildlife pond	Use plenty of oxygenating plant growth for underwater cover, with potted plants for structure.
Container pond	Use a smaller number of bunches and one or two compact potted oxygenators.
Ornamental pond	Combine potted oxygenators with water lilies and marginals for a more designed look.
Underplanted pond	Add weighted bunches quickly, then fill visible gaps with potted plants.
Pond with shelves	Use potted oxygenators on shelves and weighted bunches in open water.
Pond with no shelves	Use weighted or free-floating oxygenators in open water, and consider floating plants or a water lily if depth allows.
Pond with fish	Plant generously, but remember that fish can disturb plants and add nutrients.

What else helps keep a pond clear and balanced?

Oxygenators are important, but they work best as part of a well-planted, sensibly managed pond.

Add surface cover

Water lilies, floating plants and some other deep-water plants help shade the water surface. Shade can reduce the light available to algae and helps the pond feel more balanced.

The RHS recommends aiming to cover about half the surface area of a pond with foliage and including oxygenating plants.

Read the RHS guide to pond plants.

Useful Edenmere links:

• Water Lilies
• Floating Pond Plants
• Deep Water Pond Plants

Add marginal plants

Marginal plants soften the pond edge, add flowers and foliage, and create valuable habitat for wildlife. They also help the pond feel complete rather than simply filled with water.

Use aquatic compost, not ordinary compost

When planting basketed pond plants, use aquatic compost. Ordinary compost can be too nutrient-rich and may cloud or enrich the water.

RHS algae guidance specifically advises using low-nutrient aquatic compost when adding new pond plants.

Read the RHS guide to pond algae and blanketweed.

Avoid overfeeding fish

Fish add nutrients through waste and uneaten food. If fish are present, avoid overstocking and overfeeding, and remove uneaten food where possible.

Clear decaying debris

Fallen leaves and dead plant material break down into nutrients. Remove excess debris before it becomes sludge, especially in autumn.

Use barley straw as support, not a substitute

Barley straw can be a useful natural aid, especially when used preventatively in spring, but it should not replace good planting. Treat it as support for pond balance, not a cure for an underplanted or nutrient-rich pond.

Be careful with fertiliser

Use only suitable aquatic fertiliser, and only where appropriate. Avoid ordinary garden fertiliser, liquid feeds or loose nutrients in pond water, as these can encourage algae.

Our potted pond plants are supplied with slow-release fertiliser to support their first season. In later years, water lilies and established potted plants may benefit from slow-release aquatic fertiliser tablets pushed into the basket in spring.

Common mistakes with oxygenating plants

Expecting instant clear water

Oxygenators help support balance, but they are not an instant treatment.

Adding too few plants

A few stems in a large pond will not make much difference. Most ponds need generous planting.

Using oxygenators alone

Oxygenators are important, but they work best with lilies, marginals and other plant groups.

Treating all oxygenators as the same

Weighted bunches, free-floating plants and potted oxygenators all have different strengths. Choose the right format for the job you want the plant to do.

Ignoring pond depth

Different species suit different depths. Always check the plant label or product guidance.

Removing weights too soon

Weighted bunches are usually easiest to manage when left weighted at first.

Forgetting that plants change through the seasons

Some oxygenators grow strongly in the warmer months and may slow down or look different in winter.

Choosing invasive or unsuitable plants

Some aquatic plants can be vigorous or invasive. RHS guidance warns gardeners to choose carefully and avoid invasive plants such as parrot’s feather.

Read the RHS guide to pond plants.

Shop oxygenating plants

To choose oxygenators for your pond, start with the result you want.

For speed and value

Choose weighted bunch oxygenators.

Good examples include:

• Starwort weighted bunches
• Water Crowfoot weighted bunches
• Bunched Oxygenator of the Week

For simple open-water cover

Choose Hornwort or another suitable free-floating oxygenator.

For structure and appearance

Choose potted oxygenators.

Good examples include:

• Needle Spike Rush
• Miniature Pennywort
• Water Shamrock

For the strongest pond balance

Use a mix of weighted bunches, free-floating oxygenators and potted oxygenators, then add suitable water lilies, marginals and floating plants.

Useful Edenmere links:

• All Oxygenating Pond Plants
• Oxygenator Collections
• Pre-Planted Oxygenator Contour Baskets
• How Many Pond Plants Do I Need?
• Balanced Pond Planting Guide
• Water Lilies
• Marginal Pond Plants
• Floating Pond Plants

FAQs

Do all ponds need oxygenating plants?

Most planted garden ponds benefit from oxygenating plants, especially wildlife ponds, new ponds and ponds that feel underplanted. They provide underwater or pond-edge cover and help support pond balance.

Will oxygenating plants get rid of algae?

Not instantly. Oxygenators help reduce the conditions that favour algae by adding living plant growth and competing for nutrients, but they work best alongside surface cover, marginal planting and sensible pond care.

Are weighted oxygenator bunches better than potted oxygenators?

They are better for speed and flexibility. Potted oxygenators are better for visible, structured planting. Many ponds benefit from both.

What are free-floating oxygenators?

Free-floating oxygenators are plants that do not need to be planted in baskets. They can float or drift in the water and are useful for simple open-water cover. Hornwort is a good example.

Can I put oxygenator bunches straight into the pond?

Yes, weighted bunches can usually be placed directly into the pond at a suitable depth. Let them settle, then move or thin them later if needed.

Do potted oxygenators need aquatic compost?

If you are potting or repotting them, use aquatic compost rather than ordinary garden compost. Many potted oxygenators are supplied already rooted in a pot or basket.

Should I put gravel on top of potted oxygenators?

Where suitable, yes. Aquatic gravel helps reduce soil loss, keeps the basket tidy and makes the planting look neater.

Can I use oxygenators in a container pond?

Yes. Container ponds can benefit from oxygenators, but choose quantities and plant types that suit the size and depth of the container.

When is the best time to add oxygenating plants?

Spring and early summer are ideal because the water is warming and plants are beginning to grow strongly. RHS aquatic planting guidance identifies mid-spring to early summer as the best time to buy and plant aquatic plants.

Read the RHS guide to pond plants.

Are oxygenating plants good for wildlife?

Yes. They provide cover for tadpoles, larvae and aquatic insects, and form part of a healthy wildlife pond planting mix. RHS wildlife pond guidance highlights underwater oxygenators as useful cover for tadpoles and other larvae.

Read the RHS guide to pond plants.

Final takeaway

Use weighted oxygenator bunches for quick, flexible underwater coverage. Use free-floating oxygenators for simple open-water planting. Use potted oxygenators for visible planting, beauty and structure.

For most ponds, the best result comes from using a mix.

Oxygenators are not a magic fix, but they are one of the most useful plant groups you can add to a pond. Used generously, and combined with water lilies, marginals and other pond plants, they help create a pond that feels clearer, healthier, more natural and more alive.