To control blanketweed & other algae:
What is blanketweed?
- Blanket weed (silkweed) is the commonest form of algae.
- It is strands or filaments in the water that looks like green cotton wool.
- String algae is another form of filamentous algae that grows from the base of the pond.
- It can be picked up in a pond net, twisted on a stick or raked off.
- All algae growth thrives on surplus nutrients and mineral salts in your pond water - especially nitrates and phosphates.
- It will grow quicker the more light, warmth and food sources are available.
- On warm days in Spring blanket weed grows quicker than natural predators
- Add Daphnia or other Water fleas to eat blanketweed.
- Tadpoles also eat blanketweed in Spring - it is part of the pond ecosystem.
- Add pond plants.
Other algae growth?
- Another common algae is a green scum or thin froth on the water surface.
- New ponds often have early season problems with 'pea-soup algae'.
- This algae has no fibres in it but its microscopic cells will stain your fingers if you drag them in the water.
- This green film will normally decrease as the water matures but may take a full year to do so.
- Speed this process with Cloudy Water Treatment
- Other algae forms can look like tiny sausages or solid jelly lumps
- Like blanket weed these algae all thrive on surplus nutrients and mineral salts in your pond water & will grow quickly the more light, warmth and nutrients they have.
Algae are not what we want to see in our ponds but they are important:
- Algae cells photosynthesise so produce up to half of the oxygen in the atmosphere
- Help store carbon dioxide instead of it going into the atmosphere
- Algae are also the food base for a lot of aquatic life ie tadpoles and snails
How can I control Blanketweed & algae in my pond?
For natural algae and blanketweed control you need to remove the conditions that it enjoys:
A rich food source of nutrients and warmth.
- Nutrient control: Control the amount of rotting plant maatter in the base of the pond that releases surplus nutrients
- Do not overfeed fish and reduce fish numbers as they create nutrient-high waste products
- Avoid run-off into the pond from streams or fields that could contain fertilisers
- Nutrient use: Add oxygenating plants as the best competition for the nutrients in deep water
- Add pond plants on planting shelves that all use nutrients to grow
- Warmth and light: Shade the water to at least 50% with surface-covering pond plant leaves so it remains cooler
- Do not be tempted to position the pond in shade under trees to reduce sun levels. Tree leaves falling into the pond are a major cause of plant material rot in the base of the pond
Why has my new pond got algae so quickly?
- Algae grows quickly - quicker than the plants added to the pond you intend to have
- Your new plants will not have matured to their ultimate size so are not giving the pond the balance of growth and cover in its early days
- Plants mature at different times of year and in the early days the pond may not have all types of plant growth active
- New water in a pond takes time to mature and settle
- New plants may take time to adapt once delivered as your water pH and depths will not exactly match their previous Nursery conditions
- Because of the amount of water in a small pond it is harder to reach a balanced system. It heats up quicker than a larger volume, deeper pond.
Stop pond algae growth naturally using plants.
To keep pond water clean:
- Add the right quantity of submerged oxygenating plants to use up the nutrients.
- One third of the volume of your pond water should contain healthy, submerged oxygenating plants.
- Add Aponogeton distachyos, waterlilies and rafting plants to cover at least half of the pond surface area with leaf
- Aim to have plants peaking in growth or flowering every month of the year.
- Control the level of accumulated sediment/sludge in the base of the pond with regular maintenance - see below.
Have you planted enough plants?
- Reducing the recommended number of plants for your size of pond or planting in stages is not ideal.
- This will enable the algae to get a head start
- Adding oxygenating plants to a pond with established algae will not cure the existing problem. Actually meaning the new oxygenating plants will get covered in the algae
Prevention is better than cure or control.
Get rid of one cause of algae in a pond:
Reduce the sludge layer in the base of the pond.
- Don't let falling tree leaves and old pond plant growth fall into the pond to decay
- A thick layer of sediment sludge on the bottom of the pond is like a compost heap
- It releases nutrients - just like the nutrients released by compost from your compost heap when added to the vegetable patch.
- Treat this foul-smelling sludge on the pond base using Mud Muncher on a regular basis.
- Remove excess sediment in Autumn maintenance.
Treatment for Blanket weed and algae using Barleystraw:
As a further aid to controlling blanketweed & algae use a barleystraw product that suits your pond size:
- Barley Bio Algae Control for a small pond or container.
- If you have been treating pond algae with Barley Bio and it's still there in hot weather then increase the dose frequency, not the dose size
- Barleystraw minibales for a larger volume of water -
Each bale will float on the surface of the pond where the oxygen levels are higher and this increases the effectiveness of the straw.
- Barley minibales are most effective when held in running water - near a waterfall, pump or filter box outlet.
- These are organic inhibitors to help control blanketweed & algae growth (not killers) so not an instant fix
- Both are pet, children and wildlife friendly
We do not recommend a fast chemical fix for algae control. This may also kill useful bacteria and enzymes in the water and impact on the growth of your pond plants. It cannot distinguish one plant form (ie algae) from another.