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Are the strips you dip in the water OK to use? I mean, are they reliable enough, etc?

Huge price difference at Pet Smart - strips were like $14 and the kit with dropper bottles was $30. I don't mind spending $30, but not if the $14 route will suffice.

The strips are inaccurate.

You don't need an entire drop kit for a turtle tank. All you really need are tests for ammonia and nitrite. If you add one more a test for nitrate is handy to tell you when water changes are needed. Or just do regular water changes and skip that nitrate test.

If you have your heart set on a kit, the API freshwater master test kit is $21 on Amazon.
If you just buy Ammonia & Nitrite it's like $12 for those two combined.