Duckweed Question....

[Red Robin]

Whether you love duckweed or hate it, it tends to fairly rapidly spread and being small it can be tedious to remove.

I have once to my great surprise, witnessed a Great Pond Snail, Lymnaea stagnalis, eat a duckweed while 'walking' upside down across open water in my pond. But I have never seen this repeated.

I'm happy to keep some duckweed (it was introduced in a basket with some Japanese Water Iris I was gifted) and the beauty of having a small wildlife pond is that I can easily play God and keep all growths in balance. A bit of blanket weed is good too - It's all a matter of balance.

I use a kitchen strainer (good job I'm divorced!) to remove duckweed when it gets too much but recently I have noticed there seems to be less growing rather than more. Perhaps the Australian Swamp Stonecrop is stifling it. The stonecrop is very easy to keep under control though it might be difficult if I wanted to remove it entirely which I definitely don't want to do.

Another theory I have is that I top up my pond weekly exclusively with water from my small local river and gently pour in the water in the duckweed area - Consequently the duckweed experiences some water flow.

Another factor could be the watercress and Water-forget-me-nots. It would make a great meal for newts but I don't think they eat it.

I haven't done scientific tests but the water quality would seem to be good judging by the number of Caddisfly larvae and other pondlife which has invited itself to the garden party.

It's not a problem but I'm just curious - Anyone got any suggestions, please?

Thanks

[Red Robin]

^^^^
I don't think I made my question clear:

Does anyone have any suggestions please why my duckweed has stopped spreading and appears to have reduced?

Thanks

[GCN lova]

maybe the water flow caused them to become beached against the sides? i only have a few duckweed in my pond and they dont seem to spread.

[Red Robin]

Originally Posted by GCN lova

maybe the water flow caused them to become beached against the sides? i only have a few duckweed in my pond and they dont seem to spread.

....I'd see them if on the sides of the pond liner. Water 'flow' is minimal - A very slowly poured watering can (pipe end) so it doesn't disturb the silt on the bottom gravel - And only once a week.

Duckweed has a reputation for spreading and that's what's puzzling. I didn't think it was seasonal. I think that the vertical growth in the Aussie Stonecrop might be stifling it but I don't know. What duckweed there is looks healthy. Surely something must be known to eat duckweed. Ducks? my pond is far too small for ducks and they stay on the nearby river:

[King Edward]

Most likely it's to do with nutrient availability in the water. If nutrient levels are low (perhaps because of the growth of your Swamp Stonecrop and other plants) then the duckweed won't spread much. Normally high levels of duckweed (and/or Water Fern (Azolla) and blanketweed) indicate eutrophic conditions i.e. excessive growth of these can be symptomatic of poor water quality.

For example, I have been feeding the tadpoles in one very small pond with large amounts of fish pellets, and as a consequence the duckweed there is growing very rapidly.

I doubt that your weekly disturbance has much affect on the duckweed. Overall I'd be pleased that the pond seems to be quite well balanced, so I don't think you have to worry about it.

Edit:

Originally Posted by Red Robin

Duckweed has a reputation for spreading and that's what's puzzling.

This is because many garden ponds have excessive nutrient levels for various reasons, including fish feeding and poor tapwater quality. Likewise, many other ponds are similarly polluted through e.g. agricultural fertiliser runoff and duck feeding. In such conditions, duckweed and algae grow very well.

[Red Robin]

Originally Posted by King Edward

Most likely it's to do with nutrient availability in the water. If nutrient levels are low (perhaps because of the growth of your Swamp Stonecrop and other plants) then the duckweed won't spread much. Normally high levels of duckweed (and/or Water Fern (Azolla) and blanketweed) indicate eutrophic conditions i.e. excessive growth of these can be symptomatic of poor water quality.

For example, I have been feeding the tadpoles in one very small pond with large amounts of fish pellets, and as a consequence the duckweed there is growing very rapidly.

I doubt that your weekly disturbance has much affect on the duckweed. Overall I'd be pleased that the pond seems to be quite well balanced, so I don't think you have to worry about it.

Edit:

This is because many garden ponds have excessive nutrient levels for various reasons, including fish feeding and poor tapwater quality. Likewise, many other ponds are similarly polluted through e.g. agricultural fertiliser runoff and duck feeding. In such conditions, duckweed and algae grow very well.

....Hey, Edward! Many thanks for all that info - Much appreciated.

I am indeed very pleased with the balance in my pond. Nothing scientific in my assessment but purely based on what I see happily living and growing in it. I'm told that Caddisfly larvae only choose to inhabit good quality water. The water is very clear ('tested' by removing a jam-jar-ful and leaving it a day or two).

I reckon I only need to top it up because of the plants and some evaporation in hotter weather. Today the rain topped it up.

Apart from the sheer convenience of it, I decided to use the nearby river water so that my pond might offer a similar environment to various creatures, although I do now know that each independent body of water will evolve its own quality.

This is my water source just above a weir where a Salmon ladder is going to be built soon. Now where's that Grizzly Bear suit I've got in my wardrobe? :



My pond will be one year old in June. Who would have thought there would be so much life in it just one year later! Such a joy but somewhat addictive.

[dampflippers]

My ponds are all compltely covered with duckweed now. I can't do anything about it because each cupful contains baby newt tadpoles (or toad tads in one pond). So unless I painstakingly separate these out, I can't take any duckweed out.

Next year I will try to skim off more before frogspawn and before newts start laying.

[Red Robin]

Originally Posted by dampflippers

My ponds are all compltely covered with duckweed now. I can't do anything about it because each cupful contains baby newt tadpoles (or toad tads in one pond). So unless I painstakingly separate these out, I can't take any duckweed out.

Next year I will try to skim off more before frogspawn and before newts start laying.

....IF you don't want to wait, you might try very gently and slowly skimming with a sieve or even a small net. By carefully checking each sieveful you can return any living creatures to the water. Mind you, if your ponds are big it may take some serious time!

Note what our fellow WABer King Edward said above about the reasons for extensive duckweed though.

[Littlesparrow]

My pond seems to be producing too much duckweed at the moment, I've got some tadpoles but not many, I have been using one of those kitchen straining spoons with a long handle to remove it and checking each spoonful for tads.