shawneekots,
Desirable alkalinities for fish culture ponds typically range from 30-200 milligrams per liter of calcium carbonate. I don't have any information about S. Illinois surface waters accessable now, but I would suspect that you should be over the 10 mg/l mark. However, to test your theory, you would need to concentrate your sample. Measure a sample of water as accurately as possible and gently heat it to evaporate it down to 1/2 its original volume. (I would let the sample cool and sit for several hours before testing.) This will double the concentration of carbonates and may allow the test to "detect" the presence of carbonates. Use this concentrated sample to fill the test vial and proceed according to directions. Once you get the final result from the test, divide it by two and you should have a ROUGH approximation of your alkalinty.
