The science behind every calculator.
Every SpawnOS aquarium calculator has a complete guide here — the science it runs on, how to use it, worked examples, and the mistakes it prevents. Each guide links straight to its free, no-signup calculator.
Water Quality
Water Parameters
Water parameters are the invisible foundation of every healthy tank. This is the complete guide to what each one means, the ranges that matter, and how to match fish to the water you actually have.
Read the guide →🔬Nitrogen Cycle
The nitrogen cycle is the most important thing in the hobby that beginners cannot see. Master it and most other problems disappear. This is how it works and how to cycle a tank properly.
Read the guide →💧Water Change
The water change is the most important maintenance task in the hobby and the most commonly botched. Here is how much to change, how often, and how to do it without stressing your fish.
Read the guide →🔬Filter Size
The filter is the heart of a tank's biology, and most are chosen by a misleading box rating. Here is how to size filtration by flow and media for your stocking, not by marketing.
Read the guide →Stocking & Compatibility
Stocking Density
Overstocking is the quiet cause of half the problems in the hobby — algae, disease, aggression, and unstable water. This is how stocking actually works, and why the rule you were taught is wrong.
Read the guide →🤝Compatibility Checker
Compatibility is not a yes/no — it is a set of conditions across four factors. This guide explains how the checker scores a pairing, what its results mean, and how to act on them.
Read the guide →Chemistry
pH Buffer
Chasing the perfect pH causes more dead fish than living with an imperfect one. This is how pH actually works, why stability matters most, and how to adjust it without crashing your tank.
Read the guide →⚗️GH/KH Converter
Hardness is the most confusing pair of parameters in the hobby because there are two of them and they sound alike. Here is what GH and KH each do, why they matter, and how to convert between every unit.
Read the guide →🧂Salt Dosage
Salt is a useful tool and a commonly misused one. Here is the difference between the salt types, how to dose for disease treatment, and which fish and plants you must never expose to it.
Read the guide →💊Medication
Medicating fish goes wrong when the dose is based on the wrong volume, the meds hit the biofilter, or sensitive animals are caught in the crossfire. Here is how to treat disease safely.
Read the guide →Utility & Equipment
Tank Volume
Almost every aquarium holds less water than its label claims — and that gap quietly throws off dosing, stocking, and heating. Here is how to find your true volume and why it matters.
Read the guide →🌡️Temperature Converter
Temperature is the one parameter every fish in a tank shares — and the one you cannot compromise. Here is how to convert it, what each species needs, and why stability matters more than the exact number.
Read the guide →🍽️Feeding Calculator
Overfeeding is the most common mistake in the hobby and the hidden cause of cloudy water, algae, and ammonia spikes. Here is how much fish really need, how often, and why less is almost always more.
Read the guide →🌡️Heater Size
An undersized heater can't hold temperature; an oversized one can cook a tank if it sticks on. Here is how to size a heater properly for your tank, your room, and your fish.
Read the guide →💡Lighting
Plant lighting is sold in lumens and watts, but plants respond to PAR — and getting that wrong means stunted plants or an algae farm. Here is how aquarium light actually works.
Read the guide →