Vertex ROX .8 measurement question

[Waynerock]

Getting conflicting numbers online. I guess this stuff is strong so what is a good amount for say 63 gallon? Online I get anywhere from 1/4 cup to 1/2 cup. Always run carbon 24/7 usually use a bag of chemipure elite but since my nutrients are so low wanted to stop the ferric oxide part of CE

 

[ndrwater]

I vote 1/3 of a cup... That lands nicely between 1/4 and a 1/2.
All seriousness, ant of the above measurements will work

 

[Waynerock]

Thanks