Tool
Read Your Test Results
Four numbers and one question about the tank's age. What comes back is a short account of what that combination usually means and an ordered list of what to do — starting, every time, with testing and a water change rather than with a product.
Enter what your kit says
Pick the nearest value on each row. The options are the readings a hobby kit actually resolves, so there is no way to enter a number your test tube cannot show you.
Ammonia (ppm)
Nitrite (ppm)
Nitrate (ppm nitrate ion)
pH (pH units)
Tank age
Reading
Ammonia
0
In rangeNitrite
0
In rangeNitrate
20
BorderlinepH
7.2
In range
This is what a healthy tank looks like partway through its week: nothing at the front of the chain, and the end product accumulating as it should.
Do these in order
- Change 20 to 25% of the water on your normal day and vacuum a section of substrate.
- Record the pre-change nitrate reading — that number is what tells you whether the interval is right.
- No further action. Nothing here calls for a product.
Before anything else
If any fish is gasping at the surface, sitting on the bottom, refusing food, or showing marks or unusual coloration, change water now and then contact an aquatic veterinarian. This tool reads water. It does not diagnose animals, and nothing sold on this site should be used as a treatment.
How it decides
There is nothing clever happening here and that is deliberate. Each reading is placed in its band using exactly the ranges published on the parameter pages, which come from the sources cited there. The combination of bands then selects one of a small number of situations. The tank age question matters because the same pair of readings means something different in week three than it does in year three.
The options on each row are the values a hobby kit actually resolves. You cannot type 0.37 ppm of ammonia into it, because your test tube cannot show you 0.37 ppm of ammonia.
| Parameter | Unit | Scale drawn | First act-now band |
|---|---|---|---|
| Ammonia | ppm total ammonia nitrogen | 0 to 4 | 0.25 – 1 ppm |
| Nitrite | ppm nitrite | 0 to 3 | 0.25 – 1 ppm |
| Nitrate | ppm nitrate ion | 0 to 100 | 40 – 80 ppm |
| pH and KH | pH units, with KH in dKH | 6 to 8.6 | below 6.4 |
What it will never tell you
- What is wrong with a fish. This tool reads water. Animal symptoms are a reason to test the water immediately and then to contact an aquatic veterinarian, and nothing more than that is offered here.
- A medication, a dose, or a treatment. No page on this site publishes dosing figures for anything, including conditioners — those come from the label on the bottle in your hand.
- A product as the first move. Where a reading calls for action, the first action is testing and changing water. That is not a stylistic preference; it is what actually removes the problem.
- Anything about hardness, chlorine or temperature, none of which are in the four inputs. See pH and KH, Chlorine and Chloramine and Temperature for those.
If the readings surprise you
Before acting on an unexpected result, check the test rather than the tank: reagent dates, whether the second nitrate bottle was shaken hard enough, and whether you read the tube against white in daylight. A startling number is wrong often enough to be worth thirty seconds of doubt. My test strips and my liquid kit give different answers covers what to do when two kits tell you different things.