You can use the Hanna meter. I have one that I used to use but found that keeping it calibrated was a pain so now I just use the pH test that came in the TF-100. Which you should have, and if not you should get one. The TF-100 I mean. :)
 
I use the Hanna meter to verify, if I'm feeling color blind but not often. It is more "work" than a quick drop test. I would not buy one however, the one we have was free.

Taylor's PH (large comparator) is easier to read than HTH's OTO comparator in my opinion. I don't have Taylor's OTO so I can't compare it to the HTH OTO although I assume they are about the same. Taylor phenol red in 2oz is about $6 locally whereas .75oz is $5. Weird. The big test block was $15 and I'm glad I got it. I am regularly wrong about PH using the HTH OTO block.
 
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