I have three quarter's of back glass in four foot long tank covered with anubia attached to the glass with suction cups.(working on covering it all)
I have the same algae on a couple older leaves of anubia down lower near the substrate,but none on anubia attached to glass high on the back closer to 4 X 54 watt T5 bulb's.
I have been adding a little more KH2PO4 than usual and have not seen any evidence of more algae on other anubia plant's .
I have the four T5 bulb's hanging ten inches above the surface of the water and lighting period is eight hours.
Tryin to figure out why those anubia attached high on the glass within two inches of the surface are not showing similar symptom's as the few lower plant's, but guess I should count my blessing's.
Is low tech NON CO2 tank so maybe what little CO2 is there,is in higher concentration nearer the surface?
80 U.S gallon's dosed once a week with..
1/2 tsp KNO3
1/2 tsp KH2PO4
1/4 tsp K2SO4
1/2 tsp CSM+B
1/4 tsp Mg
It appears I spoke too soon.
Lighting mentioned above, proved to encourage spread of GSA on more than a few of the Anubia plants I have attached to the back glass, so I have since switched to three 32 watt T8 bulb's on for seven hour's.
Am also limiting phosphate for the above dosing, which I have used for last year without issues, seemed only to encourage more.
Am operating under the principal (perhaps flawed?) that if lack of CO2 is my enemy in this NON CO2 tank ,then reducing phosphate will make it the limiting factor rather than CO2.?(liebigs law)
Only been a couple week's of no PO4 other than what fish food provides, and I see no GSA on new leaves, but that which has presented itself does not appear to be leaving.
Am planning to remove the affected leaves which I am loath to do for the plant's have been with me for some year's,and resume the above dosing with the now considerably less light.
Or.. remove the plant's and soak em in 3% peroxide at four tablespoon's per ten gal for fifteen minutes,+good circulation which has worked well for me with BBA.