Types of algae growth:

A pea-soup coloured pond or one containing blanketweed or filamentous green algae (which looks like green cotton wool in the water) are thriving on surplus nutrients and mineral salts in your pond water – especially nitrates and phosphates.

Remember if the algae is the only plant form in your pond then that is the one that will grow using all the available light, warm and food sources at its disposal.

As the water warms up it grows even more quickly. Algae growth in Spring outstrips the growth of natural predators like water fleas and many pond plants.

1. New ponds often have early season problems with pea-soup algae but this is due to an imbalance between the nutrients in the water and the amount of plant growth. This algae has no fibres to it but the microscopic cells will stain your fingers if you drag them in the water. This will normally settle down as the water matures but may take a full year to do so. Speed this process with Cloudy Water Treatment

2. Some algae forms filaments or fibres that you can actually pull across the water surface as a mat (or blanket). This is known as blanketweed and this thrives on the nutrients in the pond water too.

In the short term you can remove excess blanketweed by twisting it on a stick or rake but you need to open out the twists to release any creatures and then remove the debris from the pond edge so that the nutrients in the blanketweed do not leach back to the pond and start the process again.

Algae control:

To control the growth of any algae you need to remove the conditions that it enjoys:

  1. shade the water so it remains cooler,
  2. remove surplus nutrients by adding plant growth to act as competition for the free nutrients,
  3. control the amount of rotting vegetation in the base of the pond that releases surplus nutrients,
  4. reduce overfeeding of fish that allows surplus to fall to pond base,
  5. reduce stock levels of fish as they create too many nutrient high waste products in the water

You may have a thick layer of sediment sludge on the bottom of the pond that is releasing nutrient. A bit like the nutrient levels 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 but if necessary  any sediment remaining should be removed in Autumn during maintenance.

We do not recommend chemical treatments for algae control as these chemicals breakdown the algae cells which drop to the base of the pond to add to the sediment layer which in the cycle of life means they add nutrients back to the pond that feed the next crop of algae growth.

Using chemical treatments for algae control will also remove essential bacteria and enzymes that could help the natural pond ecosystem to flourish. Ultimately you will make your pond dependent on these chemical treatments.

All products we recommend are organic or bacterial.

Prevention of algae growth using plants:

Prevention is better than cure so add the right quantity of submerged oxygenating plant growth will use up some of the ponds nutrients and so help you control blanketweed and other algae growth. One third of the volume of your pond water should contain healthy, submerged oxygenating plants.

Half to two thirds of the pond surface area should be covered with floating leaved plants (either waterlilies, rafting plants or floating plants) that give shade and spread across the surface to keep the water cool.

Keeping the water moving can also help with the some algae forms as they prefer still water so pump systems can help and if this pump is attached to a biological filter to remove nutrients and a UV light system to break down algae strands then this can help too but it is a more pricey outlay and not what many people want to see in their wildlife ponds.

Prevention using Barleystraw:

As a further aid to preventing algae use a barleystraw product that suits your pond size as this is an organic inhibitor to the production of algae growth.

Liquid Extract for a small pond or container and minibales for a larger volume of water. But this can never be a ‘cure all’ if the underlying problem of high nutrient levels is not addressed too.

Each bale will float on the surface of a pond where the majority of algae growth takes place and the oxygen levels are higher and this increases the effectiveness of the straw. Barley minibales are most effective when placed in running water – near a waterfall, pump or filter box outlet.

The concentrated liquid extract is a more instant fix for the smaller pond area. If you have been treating pond algae with Extract of Barley Straw and it’s fighting back in hot weather, increase dosing frequency, not the dose size.

Recommended products and plants: