Water Chemistry
The measurable properties of aquarium water — pH, hardness, temperature and the nitrogen compounds — and what they mean.
Doing Regular Water Changes
The core maintenance routine — how much water to change, how often, and how to do it without shocking your fish.
ConceptpH in the Aquarium
The measure of how acidic or alkaline your water is — and why keeping it stable usually matters more than hitting an exact number.
ConceptThe Nitrogen Cycle
The bacterial process that converts toxic fish waste into safer compounds — the invisible engine that makes an aquarium livable.
ConceptThe Stocking Rule
How to judge how many fish a tank can hold — and why the old "inch per gallon" guideline is only a rough, and often misleading, starting point.
ConceptWater Hardness (GH & KH)
The dissolved-mineral content of your water — GH affects fish, KH buffers pH, and together they explain how stable your tank really is.