Brown algae?

[Pieman]

Last year we replaced the pond liner and all the water. Since about July this year we have had a microscopic brown layer on the pond surface that now covers the entire pond. The water itself is not coloured other than we use a black organic dye but it’s definitely not caused by tannins. The pond has no fish just a bulrush and iris in containers with specialist pond compost. It’s impossible to scoop out the brown stuff even when removing duckweed with a net which I thought might act as a filter. When I do this the pond appears ok for an hour and then the brown layer returns. I thought the cause might be brown algae but l am not sure.

 

[Mmathis]

Hello and welcome!

I have no idea…..but why do you use black organic dye…..and what is it make from?

 

[j.w]

@Pieman could this be from runoff around the sides of your pond? Looks like everything around your pond is higher than the pond edge.

 

[Pieman]

Not sure what the dye is made from but it is excellent at giving the pond a reflective deep appearance that is quite spectacular when there is no brown stuff and is safe for pond creatures and stops blanket weed. I have used it without issue in previous years.

There certainly could be some runoff in the pond but it's not soil on the surface, I don't think. Interestingly, if you put your finger into the water the brown stuff moves away from the finger in a one-two inch circle. It reminded me of a scene from The Thing where the blood of the creature moves away from a hot object!

 

[addy1]

Welcome to the forum!

Try running your water through some filter material like quilt batting. It collects real fine debris.

 

[Pieman]

Thanks. I would need to source a pump but it sounds like that might help.

 

[Marck]

This is a biofilm.

Pond Management: Biofilm or Pond Algae?

Learn about biofilm and why it develops on the surface of ponds.

www.solitudelakemanagement.com

I'm not affiliated with this company or recommending their product, but their is some good information in the link.

 

[Pieman]

Thanks. That looks like what it is.