Oh and how the hell do you euthanise a fish? :/
An alternative that is kind to the fish is clove oil (ask your pharmacist). Put the fish in a jug, and add a few drops of clove oil. The fish will become unconscious and then die in its sleep. Make sure the jug is very well washed out before using it for other fishy tasks!
Ph is in region of 6.6 - 7.0 I would guess. Got to be a better test than these colour charts ha.