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PUREFLOW BIO / ENGINEERING FIELD GUIDE

The Aquarium Nitrogen CycleA Plain Guide for New Keepers

What the nitrogen cycle is, how to cycle a new aquarium and what to do when ammonia or nitrite appears.

Explore the process ↗Open the workbench
6 MIN GUIDEUPDATED NOVEMBER 2026
Concept illustration of a display aquarium connected to an accessible sump and filtration equipment.SYSTEM CONCEPT
AI-generated educational concept illustration; not a Pureflow installation photograph or an approved construction drawing.
01Understand the mechanismInspect the relevant process stages.
02Review the operating dutyKeep assumptions and measured values visible.
03Prepare the next decisionUse the guide, tools and project checks.
INTERACTIVE PROCESS ATLAS

See the mechanism.
Understand the duty.

Select a route or a stage to inspect the process. The cutaway explains the equipment and water environment; it is a teaching illustration, not a project drawing.

Swipe horizontally to inspect the equipment. Stage buttons below also centre the selected component.
Aquarium display and accessible life supportPUREFLOW / INTERACTIVE PROCESS ATLASCONCEPT LAYOUT · NOT TO SCALECULTURE ENVIRONMENTSOLIDS CAPTUREBIOLOGICAL DUTYDRAINAGE / COLLECTION ROUTEPLANNED RETURNMotion explains the process; it is not a measured flow rate or biological time model.
Plan the display, overflows, sump and returns as one hydraulic system.
Selected process stage

Manage the display

Record the stock, feeding and operating water volume.

How it works

Use the actual operating water volume, stock and feeding programme to establish the life-support review.

What to establish
  • Record the stock, feeding and operating water volume.
  • Keep mechanical, biological and gas duties distinct.
  • Review quarantine, maintenance access and safe water replacement.

Continue this guide ↗

Filtration mode. Wash sequence and timing are illustrative. Geometry, stage order, pipe routes and equipment configuration are conceptual. Use the approved project design, operating instructions and verified model data.

Key takeaways

  • The cycle in short: Fish and food produce ammonia.
  • A new tank has no bacteria: So ammonia can rise to dangerous levels.
  • If you see ammonia or nitrite: Do a water change, reduce feeding, and keep the filter running.
  • Keeping it healthy: Stock gradually, feed lightly and do regular partial water changes.
Reference illustration for The Aquarium Nitrogen Cycle: A Plain Guide for New Keepers
Equipment reference visual; not evidence of a completed installation.
THE SHORT ANSWER

The cycle in short

Fish and food produce ammonia. One group of bacteria turns it into nitrite, another turns nitrite into nitrate. Nitrate is far less harmful and is removed by water changes or plants.

The Aquarium Nitrogen Cycle - Pureflow Bio
Reference visual. Equipment configuration and project details must be confirmed separately.
AQUARIUMS

A new tank has no bacteria

So ammonia can rise to dangerous levels. Cycle the tank first, with no fish or just a few hardy ones, and test often. See biofilter start-up.

PLANNING WORKBENCH

Work with your own numbers.

Use the tools below to explore the relevant arithmetic. Enter measured values or declared assumptions. An estimate does not establish equipment capacity, biological performance or a safe operating limit.

Water-change volume planner

Calculate the volume changed per event and the original-water fraction remaining after repeated equal changes.

Assumptions and limits

Assumes complete mixing between equal changes. Match replacement-water chemistry and temperature; this is not a safe-change prescription or a treatment guarantee.

—Each water change · litres
—Total replacement · litres
—Original water remaining · %
Enter your values, or load the labelled arithmetic example. No design values are pre-filled.
FormulaEach change = volume × share. Original water remaining = (1 − share) raised to the number of changes.
Convert units before you calculate
Choose units and enter a value.

Planning arithmetic · inputs remain visible for review · example values are not operating recommendations

AQUARIUMS

If you see ammonia or nitrite

Do a water change, reduce feeding, and keep the filter running. Do not clean the media in tap water.

AQUARIUMS

Keeping it healthy

Stock gradually, feed lightly and do regular partial water changes.

Pureflow Bio equipment for this

Aquariums and oceanariums →Large display life support.Standard drum filters (RDF) →Automatic solids removal.
PROJECT REVIEW

Plan around the collection

Use these questions to prepare a project brief or an operating review. Check an item only when the information has been recorded for your installation.

0 of 3 checked

This checklist is a working aid in the current page session, not a saved maintenance record.

QUESTIONS

The Aquarium Nitrogen Cycle FAQ

How do I know the tank is cycled?

Ammonia and nitrite both read zero while you add a little ammonia source.

Can I speed it up?

Seeding with media from an established tank helps a lot.

KEEP READING
Freshwater aquarium→Biofilter start-up→Water quality→Aquarium Drum Filter: When and How to Use One ↗Aquarium Filtration: Mechanical, Biological and Chemical Stages ↗

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