I used Red Slime Stain Remover and the stuff was gone in a little over 48 hours. Got it from Amazon.com for a few dollars. Directions are easy to follow. I did two treatments as there was a very little red left at the end of 48 hours.
This stuff apparently drops O2 level and pH levels. I added an airstone and two wavemakers to incresae water movement while the chemical was working & I also added Marine Buffer to keep the pH up as it dropped to about 7.85 in a matter of a few hours.
The tank did fine, fish did fine, Hammer Coral did fine, flaming scallop did fine. The sand is white again.