Also, don't bother with getting a drop checker with the indicator solution. Just get the "container" if you can. You can use the API pH test kit solution too. Regardless, you need to order a 4dkh solution to make the testing accurate. Unless it is stated, most drop checkers do not include the 4dkh solution. I got mine from Ebay though after I bought a drop checker with its own indicator solution. For some reasons, it turns yellow first with the included indicator solution. I use the solution from my Tetra pH test kit instead.