particularly well to the other part of the compound. Examples include H2SO4, which is 2 H + molecules
bonded to an SO4 2- anion. This will disassociate (break up, separate, run freeeeee) in water which is what
causes the water to become acidic, (this is what H+ ions in solution do, cause acidity).
Bases, by definition accept a H+ ion from water,
ionising it to be OH-. Common bases include, NaOH.
The Na + (sodium in case you have forgotten) and the
OH- disassociate. The OH- reacts with a H+ ion in the
water to form H2O. When there is more OH- ions in the
water than H+ ions, this is when you have a basic pH.
(I may have lied to you about the ‘current’ definitions of bases and acids, but for our purposes, this is
acceptable)
Ok, cool, so we know what bases and acids are now, but how do they affect us?
Well…
You know when you measure the pH of your tank, you get a number. This number could mean anything.
Anything at all. But it doesn’t. It relates to the concentration of H+ Ions in the water. Why do we measure H+
ions and not OH-, convention. A pH of 7 is considered neutral, the H+ ions have an equal concentration to the
OH- ions, everyone is happy (fish too). Any pH that is under 7 is considered to be acidic, H+ concentration is
greater than OH- concentration. Any pH that is over 7 is considered basic, OH- is greater than H+.
The pH scale is logarithmic. This means that each number represents a concentration different to the
previous by a factor of 10. For instance, pH 6 is 10 times more acidic than pH 7 (the H+ ions are 10 times the
concentration). pH 5 is 100 times more acidic than pH 7 (fish aren’t so happy anymore). pH3 we are talking
pure vinegar (even people aren’t happy anymore). pH 8, 10 times more basic than pH7 (most fish still happy).
pH 10, 1000 times more basic (woah, what the hell are you putting in your water).
When you add acids to bases, they react, neutralising , to a degree. Adding NaOH (strong base) to vinegar is
a little like peeing on a house fire, the resulting product will be a basic salt, I guarantee it. Adding HCl (strong
acid) to NaHCO3(weak base) will leave you with an acid (carbonic acid H2CO3) and a salt (NaCl, table salt,
yum, kidding don’t eat it, its mixed in with an acid). (HCl + NaHCO3 -> NaCl + H2CO3)
How does this affect the aquarium. Well, the pH in your aquarium is dependant on a number of things. Ill try
to explain some, but others will require a google search.
Firstly, sources of bases in your aquarium. These include HCO3- (the hydrogen carbonate ion), this is due to
dissolved minerals in your water like limestone (CaCO3 ) which will react with carbon dioxide in water (which is
acidic, ill get to that I swear) to create the HCO3- ion. Plants also release the HCO3- ion when they are
photosynthesising, this is a product of consuming CO2 (carbon dioxide) from the water column and releasing
oxygen. There are countless other sources of OH- ions in your aquarium, these include shells, certain gravel,
certain rocks, fish excretions (NH3 is a base) and tap water (thanks Sydney water). These aren’t a problem in
the aquarium, due to buffers (again, I will get onto that later) which prevent large pH changes.
Acids, Acids are again, common in the aquarium. There are all kinds of organic acids that are present in the
aquarium, these are metabolites of fish waste, secretions from soil, peat juice (for lack of a better word),
present in food, put out by decaying plants, the list goes on. As a general rule, any kind of decaying organic
matter will create some form of organic acid which could affect the pH of your aquarium. Another source of
acidity in the aquarium is dissolved CO2, (CO2 + H2O -> H2CO3, H2CO3 -> H+ + HCO3-). Also, some tap
waters are acidic.