Water Gardening Questions (FAQ's) ... Blanketweed in ponds (string algae) infestation

Dear Peter J. May: I have been searching for a cure for my pond problem. We have this horrible green, slimy, stringy algae on our pond. At first other pond experts around the area told us it was from the heat or sun. Then over the winter it continued. I clean it out every day, and every day it comes back. It seems to choke out my plants after a while. We have plenty of plants that is supposed to help with that. We also have clean clear water except for the green stringy stuff. I hate it. It looks so awful and it is annoying to have to clean it out every day. We have also tried barley pads, balls, you name it. Do you have any suggestions that will help with this problem? I am getting desperate! ... Thank you Mary Young

Hello,

The person that invents a cheap cure for blanket weed infestation will become a millionaire over night. There is always some algae in natural water and some algae prefer certain conditions over and above others. You will notice that now you have blanket weed, at least you haven't got any other algae problems! I heard of a man in Birmingham back in the 60's that sold it to keep ponds clear! Anyway that doesn't help you does it?

The conditions favourable to blanket weed:

1. It loves limey water, high pH. Run off from concrete slabs, cement, soil, the lime in tap water even. If you have to top up the pool a lot, it just encourages it.

2. Topping up with tap water also feeds it the nitrates and the phosphates it seems to relish. Phosphates also come from out of the soil.

3. Blanket weed can grow at much lower temperatures than most of the competing plants in the pool and so it gets a head start on all of them. Control: First and foremost, hook out as much as you can with a rake before any other treatment.

Persistently doing this, you will find that the rest of the plant life in the pond restricts its abundance. If not ensure that you have plenty of oxygenators in the pool and lilies for cover. The pool needs to have two thirds cover by the height of the season otherwise the algae get a look in.

Otherwise you need a biological filter. If you get one of these, then using this in conjunction with a u/v and a an ecological algicide that breaks up the threads, it MAY keep the problem in order.

Dont over feed the fish and make sure that as few tree leaves as possible get in the pool keep the pool well oxygenated to encourage the right bacteria.

There are some phosphate treatments available on the market that are meant to be very good, but in general they are not effective unless the water is below pH 8. In fact I have great success with Water Wych. There is also Viresco Aqua.

They are not cheap at 15 minimum for a single treatment. Although Laguna do a sachet of volcanic rock that you float in the pool for a bit less .

Beware of standard algicides as these can make the problem worse, since the decaying matter that is dead blanket weed makes the perfect fertiliser for new growth.

Hope this helps you get on top of it.

Pete

PS Snails love it too.