Did you try
citric acid? It is great for salt deposits, and might work for your coraline. I use BRS citric acid on my pumps, lids, and plastic parts. The BRS product is "food grade."
For pumps, I place them in a bath of citric acid and run them. For crusts, I use citric acid on a tooth brush.
On glass, I apply citric acid to a thick paper towel at the sink while rinsing with warm water.
For rough crusts, soak the item.
After cleaning, I rinse liberally with distilled water and wipe with a paper towel.
Hydrogen Peroxide (H2O2) is a great disinfectant. I am not sure how it does on coraline. I do use it in a syringe to kill green algae at the front glass sand junction. I suspect it might kill coraline algae, but not ease its removal.
I have read of using
50/50 water and distilled white vinegar ; however, I have never tried it.
There is also a R2R thread :
How do I get rid of Coralline Algae?
I look forward to hearing your solution,
JIm