Rocks and sand covered in red. Dino/cyano/other?

[vetteguy53081]

What strength of peroxide? Typically it's 3% or 12%?

3%

 

[KonradTO]

In the end I decided to go for 3 days blackout+manual removal+uv light and I must say it seems it worked quite well.
Now has been 2 weeks since the treatment and I had a decent tank since then