I think that a PH pen is a must to avoid major problems and get better results from your grow. I mean if he has a PH of 8 right out of the tap then he may get so many defs that he may not even bring his plants threw a harvest and if he does he may get half of the yield that he could of. Not even good nutes can make up for bad PH and nute lock out.
If anything, recommend the PH strips that you find in aquarium departments like in Wal Mart.
Adieu