Can DOC be measured in planted tanks?

C

chefkeith

Loach Inspector
Aug 17, 2003
674
0
16
Detroit
After reading some threads about water changes and nitrate levels; I wonder if there is a way to measure DOC levels? Would a TDS meter measure aquarium pollutants?

On my main tanks (which are connected together), when I do a water change it's usually between 55 to 100 gallons that I replace. Which is between a 15-25% weekly change. My nitrate levels are usually only around 10ppm because 2 out of 4 main tanks I have are fully planted.
 
not a chemist, but have a guess. since Total Dissolved Salts are by definition of 'salt' largely ionic in nature, a TDS meter might not be able to register the carbon rings and strings of organic compounds, aside from those with ionic-acting functional groups.

i imagine there is a test for DOC's but might take some lab savy.

i've actually wondered this myself, and i hope you get a more complete answer....

:cool:

edit: liv and i posted at the same time... hehe no response for over a day, and two at once. funny
 
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Would a TDS meter measure aquarium pollutants
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the short answer is NO. in any event most dissolved solids are not "pollutants" in an aquarium. many dissolved solids are inorganic compounds which exist as ions in solution, the most common of these ions are:

cations = Calcium, Magnesium, Sodium, Iron, Manganese
anions = bicarbonate, chloride, sulfate, nitrate, carbonate

in order to measure dissolved organic compounds you'd need equipment only found in a chemistry laboratory.

if you maintain your nitrates at ten ppm or less, you can be assured that your DOC levels are just fine.
 
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liv2padl said:
in order to measure dissolved organic compounds you'd need equipment only found in a chemistry laboratory.
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Couldn't a protein skimmer be used to somehow measure
DOC's.

liv2padl said:
if you maintain your nitrates at ten ppm or less, you can be assured that your DOC levels are just fine.
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Are DOC's good or bad for a planted tank?
 
DOCs are always present in a mature tank. Excessive DOCs, like excessive nitrate, NaCL, and so forth are not good to bad, depending on the particular DOC and the concentrations. If you do good water changes, dissolved organic compounds are not an issue, nor is nitrate.

Protein skimmers (foam fractionators more accurately) do not work well in FW (surface tension) and are not quantitative in any case.
 
Not to minimize water changes, but there’s also DOC (or DOM-dissolved organic matter) in you tap water. Where do you think all the remains of bacteria, algae and such go after the added disinfectants kill them? :) Various sorption methods remove some but not all DOC from the water system.


Tom
 
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