Guides
Long-form guides that explain the reasoning, not just the rule. Each one lists its sources, shows its arithmetic, and marks the places where we still owe you our own measurements.
Cycling
Fish-In Cycling: How to Protect Fish in an Uncycled Tank
Fish already in an uncycled tank? A harm-reduction plan: daily testing, water change thresholds, lighter feeding, and honest caveats about ammonia binders.
How to Fishless Cycle a Tank Using the 2 ppm Ammonia Method
A step-by-step fishless cycle: dose ammonia to about 2 ppm, track nitrite, avoid stalls, and confirm the tank clears ammonia in 24 hours before adding fish.
The Aquarium Nitrogen Cycle Explained: Ammonia to Nitrate
How ammonia becomes nitrite and then nitrate in an aquarium, which microbes actually do the work, and how temperature, pH, and alkalinity change the process.
Stocking
How Many Fish Can a 20-Gallon Tank Hold? A Worked Approach
Stock a 20-gallon aquarium by real water volume, bioload and behavior, not inches. Covers 20 high vs 20 long, net gallons, and five example stocking plans.
Why the Inch-Per-Gallon Rule Fails, and What to Use Instead
The one-inch-per-gallon stocking rule ignores body mass, footprint and behavior. See the math behind its failure and a better method checked with nitrate tests.
Water Chemistry
Aquarium Test Kits Explained: Liquid, Strips and Digital Meters
What aquarium test kits really measure, why NH3 and NH3-N readings differ, accuracy traps in liquid kits and strips, and how to check a kit against a standard.
GH, KH and pH Explained: Hardness, Buffering and Safe Changes
GH, KH and pH for fishkeepers: dGH to ppm conversions, how KH buffering prevents pH crashes, the CO2-pH-KH link, and safe, gradual ways to adjust your water.
Maintenance
Quarantine Tank Guide: Setup, Observation and When to Get Help
Why and how to quarantine new aquarium fish: equipment list, the pre-seeded sponge filter trick, how long to observe, what signs to log and when to call a vet.
Water Change Math: How Much and How Often to Control Nitrate
Derive the steady-state nitrate formula, size weekly water changes to stay under about 20 ppm, and account for nitrate already in your tap water.
Equipment
Aquarium Filter Flow Rate: Rated vs Real Turnover Explained
How much flow does your filter need? Why rated GPH overstates real flow, how to measure turnover, and flow targets for planted, community and betta tanks.
What Size Aquarium Heater Do You Need? Watts, Delta-T and Safety
Size an aquarium heater from the gap between room and tank temperature, not watts per gallon alone, with worked examples, two-heater setups and safety tips.
Planted Tanks
Low-Tech Planted Tank Setup Without CO2: Plants, Light, Soil
Set up a planted aquarium without injected CO2: hardy plants, sensible light duration, inert or capped-soil substrate, simple fertilizing and algae balance.