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Growing rapidly, even in winter, across the bottom of the pond ( 150 cm) and upwards covering many plant baskets is a bright green algae-like (that is, there are no discernible leaves) plant. I have reeled in, in one continuous piece!, about two metres of it. Plenty left. Evidently it has come in on one of the plants I bought. Is this stuff I should get rid of; will it stifle the plants as they regrow after the winter, or will the fish I intend to introduce eat it or like to hide in it? However, I can see it covering the whole bottom ( not unwelcome) and every plant basket. The pond was only planted last autumn. Anyone know what this is? Many thanks.

Mike, you seem to have a strong growth of blue-green string algae in your pond. It's also called blanketweed, because it can totally cover plant baskets and even their contents. A little string algae is acceptable, because it's a fine place for your pond fish to lay their adhesive eggs, and an even better place for the young fry to hide from predators (like their own parents). But if it grows past that point it can smother your underwater plants and kill them off. Blanketweed is one of the few algae that fish won't eat, so you'll have to get rid of it manually.

Early spring is when all kinds of algae grow in ponds, spurred on by the warmer water and greater day length. The most common are the single-cell algae that float through the water and turn it green. The string algae that you have form long chains of connected cells instead. They're the strings you see, just one cell wide and very long.

As I explained in your earlier question, algae growth will diminish and then stop when the more advanced vascular underwater plants start growing. Their growth will deprive the algae of the necessary nutrients, and their shade will deprive the algae of the necessary sunlight.

Until then, you're doing the right thing to protect your oxygenating plants by reeling in as much of the string algae as you can. We've found the easiest way to capture blanketweed is to rotate something like a toilet brush in their midst. Keep twisting the brush and pulling it out of the water, then pull the blanketweed off the brush. You can either throw the algae away or add it to your compost pile. If you keep after it, your underwater plants will soon safely continue oxygenating the water for your fish. Adding more oxygenating plants should prevent any future infestation of blanketweed. Good luck.

Suzanne and Peter

Dear Suzanne & Peter

thank you so much. Your description fits exactly. I am glad you have so much knowledge. I shall start reeling first thing tomorrow.