Today, I am posting a bit about blanketweed and algae. There is blanket weed in most of my ponds. I have found over the years that blanket weed comes in different forms and stages. Most of the blanket weed I have at the moment is at the stage of where it starts to die off and float (see pic below), and can be easily removed with a net.
I know that in some ponds blanketweed can be absolutely everywhere but right now in my ponds, it is more sporadic, with some plants being more affected than others. Potamogeton gayi, P. lucens and P. crispus, for example, seem to have less blanketweed around them while Elodea has significant amounts and, to some extent, so does giant Vallisneria.
Maybe I am wrong, but at the moment I am going by the theory that healthily growing plants might be less troubled by blanket weed. Vallisneria (giant Vallis) has not yet started to grow and tends to have some blanketweed. I am hoping that as the weather gets warmer, the Vallis will take off again and might have less blanketweed on its leaves.
I recent wrote about Elodea;
I planted my Elodea in baskets with clay topsoil and placed them at the bottom of my ponds (80cm depth). I read the other day in one of my Ada Hofman reference books that in her experience, Elodea does better on a shallow marginal pond shelf and that if it is planted deeper than 20cm, the stems become too long and thin and easily break off, causing the plant to become a nuisance by multiplying too much. I am thinking that this might have happened to me, as I find many of the plants not looking too healthy and it is also exactly those plants which seem to have mbore blanket weed around them.
I have started removing some of the Elodea baskets from my ponds anyway, as a way of thinning them out. I feel I can afford to do this as I still have enough other pond plants left and perhaps this might even encourage some of the others to grow more.
I will cut back the Elodea in some of the baskets and then place them on the shallow shelves and observe the diference. I will also start grouping the Elodea baskets together more tightly, more away from the other baskets, to prevent them from invading other plants.
Over the last couple of weeks, I have been thinning out Elodea from most of my ponds. In three of the ponds (big pond at the back - middle pond - and the one in between) I removed half the baskets of Elodea altogether and the remaining baskets of Elodea I cut back.
Here is an example of a more unhealthy looking basket of Elodea. Baskets looking like this I removed;
This example is in better shape. Baskets like this, I kept and trimmed right back;
I also fertilised the baskets but not all of them, so that later on I can tell the difference in plant health and perhaps even if they might be affected by blanketweed differently;
I am hoping that the other plants in the ponds might perform better also, with less competition from the Elodea. Cutting back the Elodea so hard is an experiment for me as I have never been so ruthless before in removing so much plant mass in one go. I am aware that I run the risk of a backlash in the form of an explosion of algae or blanket weed over the coming weeks but I am counting on the fact that I still have a large amount of baskets remaining and hope that these will be spurred on by removing competition from Elodea.
Another reason for cutting back the Elodea is that I wanted more growing space for the other plants. It was useful in the beginning to have access to lots of Elodea to control the algae but now I have a more varied and greater stock of other ponds plants, I really want to try out different combinations and groupings to see what can be achieved visually, as well as practically in terms of keeping a healthy pond.
If cutting back the Elodea proves to be a succesful way to maintain the vigour of the plant, I will certainly do so earlier next year as newts have already returned to the ponds, so it was not really a great time for me to be removing plants during their breeding season.
Here a few pictures of inside the ponds.
The large pond at the back is definately a success story. Probably I think because of the ratio of deeper parts (80cm) to shallower parts - this pond has the largest ratio of deeper water and least amount of blanket weed, especially now the Elodea has been removed which had quite a bit tangled among it. It has baskets of Elodea, Potamogeton lucens, P. crispus, giant Vallis, and Myriophyllum 'Red Stem';
The next pond towards the front is a smaller pond, which sits between the large pond at the back and the middle pond. Potamogeton crispus does very well in this pond, as it does in the large pond at the back. There is also some Vallis in here. I removed Elodea and replaced with baskets of Potamogeton lucens and Myriophyllum 'Red Stem'. This pond is probably the most shaded out of all of them but is only shaded for part of the day. There is also hornwort in this pond which prefers the shade. Unfortunately, hornwort disappears easily during blanketweed removal (hornwort is not rooted and therefore easily gets caught up with blanketweed being pulled out).
I forgot to take a picture of the middle pond but will share a video at the end of this post, which shows the middle pond. This pond had the most Elodea growing and the most amount of blanketweed also. I removed two thirds of baskets of Elodea and added baskets of Potamogeton lucens and Myriophyllum 'Red Stem'. It also has Vallis.
The pond next to my house is also doing well. Here you can see how the blanketweed seems mainly concentrated around the Elodea at the top of the picture, and to some extent the Vallis (bottom/left). The Potamogeton gayi, P. perfoliatus and P. lucens (right/bottom right) seem less affected. I have thinned out the Elodea in this pond but thought I should 'play it safe' in at least one pond and did not cut back drastically as I have in the others. Also, it will be interesting to see if the blanketweed might just disappear by itself.
One pond where things have not gone too well, is the smaller pond which sits in between the large pond at the front and the middle pond. This pond contains a population of Aphanius mentho. Here is a video taken back in March, where you can see some of them.
The problem is that the water over the last three weeks is turning green and I need to take some urgent measures.
18 April 2022;
24 April 2022; I noticed water starting to turn a bit 'milky'
08 May 2022
I am not sure what is causing this problem. I did not remove Elodea baskets from this pond, nor did I remove other pond plants, which otherwise would have been an obvious explanation.
The Aphanius mentho population was becoming a bit large, with too many youngsters from last year. A high bio load could cause problems, especially without filtration but on the other hand, these are still small fish. Also, I do not feed the fish in my ponds, so I wonder how much bio load can really be added to the system?
When the water at first was turning a bit 'milky', I did think whether this could be caused by bacterial issues and was wondering whether the cause might be a dead animal or something fallen into the water which might be polluting it or something? But I can't detect any foul smell and there has been no scum floating on the surface.
Last year, I did not have any problems with green water.
Whatever the cause, I need to add some more oxygenating plants to combat the green water and maybe even install some shade netting. For now, I placed another basket of Elodea in there, both to compete against the green algae in the water and provide more surface cover.
I will leave you with a video with more views of inside the ponds. In future updates, I will share more about the individual types of submerged/ oxygenating pond plants, as well show pics of the rest of the garden which is really starting to look great, and of course let you know how I am getting on with the green water in the mentho pond.