Nitrate and pH in a Fishlessly-cycled Aquarium

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SUMMARY

The discussion centers on the relationship between high nitrate concentrations and pH levels in fishlessly-cycled aquariums. It is established that a nitrate concentration of approximately 80mg/l can influence pH, particularly in low-buffered water. The conversation highlights the potential formation of calcium nitrate, which can introduce additional H+ ions, thereby lowering pH. The oxidation of ammonia to nitric acid is also noted as a possible contributor to acidification.

PREREQUISITES
  • Understanding of nitrogen cycling in aquariums
  • Knowledge of nitrate compounds, specifically calcium nitrate and magnesium nitrate
  • Familiarity with pH buffering systems in aquatic environments
  • Basic chemistry of acid-base reactions
NEXT STEPS
  • Research the effects of high nitrate levels on aquatic ecosystems
  • Study the chemistry of calcium nitrate and its impact on pH
  • Learn about buffering agents like bicarbonate in aquarium water
  • Explore the nitrogen cycle and its implications for fishless cycling
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Aquarium hobbyists, aquatic biologists, and anyone involved in maintaining water quality in fish tanks will benefit from this discussion.

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Homework Statement



Prior to introducing livestock, a fishkeeper may establish colonies of nitrosifying and nitrifying bacteria by repeatedly inoculating an aquarium with a solution of ammonia (to simulate the presence of fish). At the end of the process there is a high concentration of nitrate in the water - typically of the order of 80mg/l.

May such a concentration of nitrate lower pH?


Homework Equations



[none understood]

The Attempt at a Solution



And anyway, what kind(s) of nitrate is it? Cations can come only from the virgin water (usually tapwater) in which there is typically a preponderance of calcium and magnesium. Is calcium nitrate more likely than magnesium nitrate? I have read that the former's pH is around 4 or 5 ; while the latter's is around neutral. So if calcium nitrate forms there'll be a heap of extra H+ ions around ...

... which is fine so long as there's sufficient buffer (in the form of bicarbonate) to soak them up. If not, then presumably high nitrate in low-buffered water would indeed tend to acidify? Would nitric acid form?

Or am I on the wrong track altogether?
 
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The only thing I can think of is that oxidation of ammonia can acidify the solution:

NH3 + 2O2 -> HNO3 + H2O

You don't produce calcium or magnesium nitrate, these cations were in water and they are still there, nothing have changed.
 

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