Lost Red Sea PH Vial - How much water??

[GettingFiesty]

Lost the vial that goes with my Red Sea Ph Test. Have the instructions, but they only say...Fill vial to the line. Does anybody know how much water to use with my two drops of phenol red/

Thanks.

[rvitko]

The standard of most test kits is 5ml.

[GettingFiesty]

Thanks!