Brown slime on edges of water lily pads?

[petersexton]

G'day from Perth, Western Australia,
We've had our 5.5k litre pond for years! We used to have koi, but now we have goldfish and barbs.
Recently, I have noticed a brown slime developing on the edges of some lily pads. It will grow towards the centre slowly, and will eventually kill the leaf.
I've never seen it before and can't identify it (yet) on google.
An interesting feature is that it wipes off with a little rubbing and if it's fairly new, it leaves the leaf looking fine!
I attached a before (with brown edges) and after wiping, photos.

I'd appreciate if anyone can identify it. And how to get rid of it would be very useful, too!

Our pond is crystal clear and has perfect water che
mistry (except maybe for pH, because that fluctuates all the time).

 

[GBBUDD]

Lilies loose there leaves all the time as they start to fade they are not there healthies so its no surprise some algae would get a hold.

 

[Lisak1]

I'm with @GBBUDD - it just looks like aging lily pads to me.

 

[petersexton]

Of course, thank you.
I am just surprised I have never seen this particular presentation. I've seen blanket weed, string algae, and green water, but never this brown slime around the edges of what otherwise appear healthy leaves. Maybe I just never noticed!

I try to regularly remove all leaves that change colour, are visibly, seriously damaged, or have damaged stems! These leaves, with the brown slime on the edges, however, often show no other indication of deterioration. Could it be a specific algae that attacks in this way?

 

[j.w]

@petersexton

 

[Lisak1]

@petersexton - sure. Except for the "attack" part. Algae just grows. And a pond changes constantly. When a new variety starts to thrive, the old algae will just disappear. Make sure you're keeping the pond free of any organic material that might be contributing to the growth of algae and things should take care of themselves.

But again - these look very much like my lily pads when they age out.

 

[petersexton]

Thank you.
I'll stop worrying now!