As you all know, this is a huge topic and it is daunting for most people, new to the hobby or otherwise. I
figured I’d put together a bit of writing and see if I can explain it as best as possible, because I feel it is
important for anyone who is just starting up or has been running a planted aquarium to understand what is
going on, why things happen and what you need to do about them. Hopefully, this is helpful to those who don’t
quite get the intricacies of chemistry.
Just a note on the order of things included here: I put it so that inexperienced people can start with the first
section first, it will explain the basics, the second section will explain the nitrogen cycle in detail, the third
section will be briefly on CO2 and Oxygen, the final section will be on plant nutrients. I guess it is ordered from
most known to least known and if you know a section, don’t bother reading it, I haven’t added anything ground
breaking or experimental, I simply recapped the basic chemistry in easy to grasp terms.
1. The Basics
Basic Elements in the planted aquarium include- Iron (Fe), Magnesium (Mg), Boron (B), Copper (Cu),
Manganese (Mn), Sulphur (S), Nitrogen (N), Hydrogen (H), Oxygen (O), Calcium (Ca), Potassium (K), Sodium
(Na) ,Phosphorous (P) and of course Carbon (C), I may have missed a few which I will edit in later, but these
are the ones that I can think of as most important.
Ions- Charged form of an element or a compound (compounds being a series of elements bonded together in
a fixed ratio). Ions can bond together to form Ionic Compounds. There are two types of ions Anions and
Cations.
Anion- A negatively charged ion, examples include Nitrates (NO3-), Phosphates (PO4 3-), Nitrites (NO2-)
and Sulphates (SO4 2-), Carbonate (CO3 2-)
Cation- A Positively charged ion, normally a metal (Ammonium is an exception, there are others), Examples
include Ca 2+, Fe 3+ Fe 2+ (both iron, but differing oxidation states, will get to this momentarily), Mg 2+, H+
(hydrogen is mostly thought of as a non metal, I am content to leave it this way as an exception to the rule)
and ammonium is NH4+.
Compounds- A chemically bonded species consisting of multiple different elements, can be ionic (Na + Cl - ),
can be charged (SO4 2-, NO3 -), can be stable (H2O, O2, CO2) .
Bonding – There are multiple different types of bonding that go on in an aquarium, however I will explain only
Ionic Bonding. This is how ions come about. I will first use an example, elemental Magnesium isn’t particularly
stable, it will react with most things (air, water, acid, your fishes poo), it can however stabilise itself by donating
its two electrons to another unstable compound, say sulphuric acid. You will never ever ever find Magnesium
in its pure form in the aquarium, (call me if you do, I’d like to see it :P), however you will find Magnesium
Sulphate in just about every aquarium. This is a Magnesium cation bonded to a sulphate anion, it is stable and
will dissolve in water due to being ionic (I can explain this more if someone wants, but this should be sufficient)
OK, with that out of the way, I will have a crack at describing water parameters.
pH
pH is a measure of the acidity of the water. A pH of 7 is considered neutral. At this point, the acid causing H+
ions have equal concentration to the base causing OH- ions. Hangon, what ‘s an acid and a base?
A substance is classed as acidic if it can ionise water by giving water a H+ ion, which will form H3O+, this
however does not mean that any substance containing hydrogen will turn your water into a bubbling pool of
acidic water, in fact most hydrogen containing substances are content to sit and do nothing. The compounds
you have to worry about are called Acids, and they as a general rule, will contain a hydrogen that isn’t bonded