I tried your method on my 25 gallon tank; it had what was probably the same type of staghorn algae ("Staghorn on Steriods"
)that you described in post #1. This time I dosed 3.5 tablespoons per 10 gallon since the algae was pretty bad; after about 2 hours ALL the staghorn turned red and so far no issues with fish and shrimp (Though the shrimps are a shaken up a bit from the massive flow). Pictures are attached. I wasn't able to get any pre-treatment pictures because I forgot, sorry, but it's pretty much the same thing in the pictures, just the color is gray to black. Thank you for sharing this technique! I will update it in a few days to show you the overall result.
Got a bit artsy on one