Flat black algae - removal advice

[LFNfan]

I'm not averse to a bit of algae but want to do my anubias a favor and get rid, somehow, of this black algae on its top leaves (near the surface where my ottos and SAE do not venture). It's been there a while.

This stuff will not budge even under firm finger rubbing. What little comes off appears dark green on the finger.

These leaves are above the water during water changes, so I could try alcohol, or something else.

Any advice much appreciated.

 

[hypnogogia]

If they’re above the water line at water change time, you could try brushing some liquid co2 onto the leave, which, btw. look like you have some form of nutrient efficiency.

 

[LFNfan]

Thanks hypnogogia. Something like this?

The 'variegated anubias' is an older leaf that doesn't let me forget that period of iron deficiency. That's more or less better now and newer anubias leaves are properly green. Now you mention it the floating plants do look yellowish in the picture but they much look more healthy in real life!