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Green algae on pond

I have inherited what I think is a very old cattle / animal watering hole which is a pond in winter but dries up to a bog in summer. The water reaches about 5 feet deep at its deepest end where the sides are supported by a stone wall but the remainder becomes progressively shallower meaning the water has ample chance to warm up at the edges. Because of its size and also because it has a wall at one end, I thought I would leave it without a lining and so I have just cleared and planted up the banks abutting its edges. However, it has a mud base which i think would make fabulous soil for the garden but is far from ideal for the pond because I suspect its highly nutritious. I really don't ideally want to have to line it but I don't know if it is possible to keep it as a pond / bog garden otherwise. I have no plants as yet in the pond (I suspect this isn;t helping the algae situation) because I didn't know what would thrive in both a bog and a pond. Any thoughts gratefully received. BTW I have never cared for a pond in my life but am a reasonably knowledgeable plants woman!


  • a1154a1154 Posts: 1,073
    I have something similar, (unlined natural pond) it’s pretty deep at the moment but gets very shallow in summer. Never completely dries out though. You don’t need a liner as long as you are ok with the levels changing like that. I get algae blooms, its natural and comes and goes, it’s clear most of the time. 
  • Thank you for replying. I wouldn't be so bothered about it if there was some pond life but having pulled out a lot of the slime I cannot see much living in the pond. There are no frogs, toads snails or minibeasts that i can spot, just green sludge and mucky water!
  • JellyfireJellyfire Posts: 1,139
    Plants plants and more plants is the key to clear water and pond life. I’d just get your hands on as many natives as possible, throw some in and get some marginals round the edges and the water will probably sort itself out. If it was a cattle pond then it’s probably packed full of nutrients at the moment.
    As it’s a soil/clay and presumably quite large you should be wary of anything too invasive.

    Somebody recommended the devonpondplants site as having good info on plants and their tendency to be invasive, and I’ve found it useful 
  • a1154a1154 Posts: 1,073
    Hmm that’s interesting jo, I assume it’s been there a long time? But just stopped being used by cattle? I found ponds super quick to get wildlife. After some research i decided to add no plants at all. Depends what you want to end up with. 
  • Jellyfire
    Thank you for replying and the name of the plant seller. I've had a quick look on their site and have decided to phone them (after work!) to ask for suggestions, as my main concern in planting, is that the depth goes from bog to 5 feet depending on the time of year! I know that i can control this to an extent by creating shelves etc and also adding water if the pond starts to dry out but I already have a large area to maintain and I was hoping to be able to create a wildlife area and then let it manage itself as far as possible.
  • a1154
    It hasn't been used by livestock for at least 25 years but yes the soil under the water is very firtile. The only wildlife I have seen are ducks and some large geese which I am assuming have eaten any spawn / insects that may have arrived. Although I love birds I would like to encourage other wildlife too. 
  • JellyfireJellyfire Posts: 1,139
    Ponds that change level are great for a lot of wildlife, some even depend on them drying out completely. There are lots of plants that will be fine with a radically changing water level, but phoning a decent specialist is very good idea. Also presuming it’s pretty large you will want to be getting some good rates on any bulk purchases so it doesn’t cost you a small fortune. 
    Good luck with it (and photos would be nice if you have any, always love seeing other people s ponds)
  • Thank you for all your help. These aren't good pictures but all I have that show the pond before it flooded its banks this winter. 
    You can just see the retaining wall on the far side. It's still quite bare as I only cleared the nettles docks etc last summer. I think a further problem which is exacerbating algae growth is the run off rain water from the surrounding field. 
  • JellyfireJellyfire Posts: 1,139
    Wow what a lovely looking spot for a pond! So you say the water level rises and drops a lot, does it come up to cover the whole muddy area, or is that just from walking around on it?

  • It has flooded up to the blue grasses and will do this each winter. It can't reach any higher because there is a flood pipe system at the other side of the pond. However, the fluctuating water levels make planting it difficult because I have to find plants that survive in water levels that range from about 18 inches to nothing where the muddy area is in the picure. Also at its deepest, where I have put large stones to try and keep water in, the level can fluctuate from about 5 feet at its deepest in winter to a muddy swamp in the height of summer. I have bought a lily, a carex and a couple of other plants which require varying depths but I am wondering how best to manage this? Any suggestions?
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