Something looks wrong in your freshwater aquarium. You can see the problem, but you may not know what it is called or what to check first.
Freshwater Aquarium: What to Check Next is built for that exact moment.
Instead of starting with a diagnosis, this troubleshooting field guide starts with what you can actually observe: fish hiding at the bottom, gasping at the surface, cloudy water, white spots, torn fins, unusual swimming, equipment trouble, or a problem that starts after a water change or new fish.
Find the problem in ordinary language, then follow a practical route:
- What you see
- What to do first
- How to check it
- What to do if the result is abnormal
- What to check next if the first result is normal
- When the problem needs more help
Inside you'll also find:
- A 5-Minute Tank Triage for urgent tank-wide problems
- Direct ammonia and nitrite response guidance
- Fish behavior and visible-health troubleshooting routes
- Filter, heater, aeration, and power-failure checks
- Water-change and new-fish problem routes
- Algae, growth, plant, and unknown-organism pathways
- Compatibility and test-record worksheets
This is not a disease encyclopedia or a start-to-finish aquarium setup manual. It is a compact troubleshooting reference for the moment you are asking:
"Something is wrong. What do I check next?"