Logging water tests

You can keep a history of your water tests by logging them to a saved tank in the Tank Builder. Each reading is stamped with the date and time you log it, can carry a short note, and appears under Recent readings for that tank. Logging needs an account; the Water Check page itself never saves anything.

Where do I log a water test?

Logging happens only in the Water test tab of the Tank Builder (or the built-in Tank Builder on a tank size guide page). The standalone Water Check page has no log button and doesn't save your numbers.

You need to be signed in. If you're not, the Water test tab shows "Sign in to log readings and track your water over time." Tap Sign in; you'll come back to the Tank Builder afterward.

How do I log a reading to a saved tank?

1. Open the Tank Builder and tap your tank under Your tanks to load it.
2. Switch the results panel to the Water test tab.
3. Enter your results under Enter your test results (Temperature, pH, Ammonia, Nitrite, Nitrate, GH, KH). Fill in only what you tested.
4. Under Log this reading ("Adds a dated entry to "[tank name]" so you can watch changes over time."), add an optional note.
5. Tap Log reading.

You'll see "Reading logged." The note box clears and the reading appears at the top of Recent readings. The values you typed stay in the boxes, so you can compare with your fish's needs; clear them yourself before your next test.

Can I log a reading without saving a tank first?

Yes, in one step. If you haven't saved or loaded a tank, the box is titled Track this over time and says "Readings attach to a saved tank. This saves your build and logs the reading in one step."

1. Enter your results (and an optional note).
2. Tap Save tank & log reading.

The builder saves your current build as a new tank (using the name in the save box, or a name based on its size, or "My Tank") and then logs the reading to it. This counts toward your 4 saved tank limit. If you already have 4 tanks, nothing is saved or logged, and the message "You've saved 4 tanks" appears in the save section under 3. Save your build (scroll up to see it on a phone). Load an existing tank first, or delete one. See Saving and sharing tanks.

What can I record in a reading?

Each reading can include any of these, all optional, but at least one value is required:

• Temperature (°F)
• pH
• Ammonia (ppm)
• Nitrite (ppm)
• Nitrate (ppm)
• GH (dGH)
• KH (dKH)
• Note: free text up to 200 characters (placeholder "Optional note (e.g. after a 30% water change)")

GH is saved with your reading even though it isn't graded. Temperature must be in Fahrenheit; convert Celsius first (multiply by 9, divide by 5, add 32).

The log button stays grayed out until you've entered at least one value. If you somehow try with an empty form you'll see "Enter at least one value first."

When is a reading dated?

A reading is stamped with the date and time at the moment you tap Log reading. You can't choose a different date or time, so log right after you test. If you're catching up on old tests, add the real test date in the note (for example "tested Sunday").

Dates show in your device's local format, for example "Jun 16, 2026 · 3:40 PM."

Where do I see my past readings?

1. Load the saved tank in the Tank Builder.
2. Switch to the Water test tab.
3. Scroll to Recent readings.

Each entry shows the date and time, a one-line summary of the values you recorded (for example "Temp 78°F · pH 7.2 · Ammonia 0 ppm · Nitrate 10 ppm"), and your note in italics if you added one. Values you left blank aren't shown.

Recent readings appears only when a saved tank is loaded and it has at least one reading. Each saved tank has its own separate history; readings never move between tanks.

How many readings are kept?

Recent readings shows the latest 20 readings for that tank, newest first. Older readings aren't deleted; they just aren't shown in the builder. To see every reading you've ever logged, use Download my data on your Account & data page, which includes all your tanks and water readings. See Privacy and your data.

There's no chart or graph of readings over time, and no limit on how many readings you can log.

How do I delete a reading?

1. In Recent readings, tap the trash icon on the right of the entry.
2. Confirm "Delete this reading?"

The reading is removed permanently. If it fails you'll see "Couldn't delete that reading." Try again.

Can I edit a reading?

No. Readings can't be edited after you log them. To fix a mistake, delete the wrong reading and log a corrected one. Note that the corrected one will carry the new date and time.

Does logging water tests earn bubbles?

Yes. Logging your first ever water reading earns bubbles once. Logging at least one reading in a week also earns bubbles, once per week (weeks run Monday to Sunday, in UTC time). See Bubbles.

Logging many readings in the same week doesn't earn extra weekly bubbles.

Can other people see my water readings?

No. Water readings are only shown to you, in the Tank Builder, when that tank is loaded. They don't appear on a public tank page, your profile or the feed, even if the tank is public.

What happens to readings if I delete a tank?

They're deleted with it. The delete confirmation says "Delete "[name]"? Its water test history goes with it." Download your data first from Account & data if you want to keep them.

What does the Water test tab tell me about my reading?

As you type, the tab grades your numbers (red, amber, heads-up or green) with a banner: "Something needs attention now," "A few things to keep an eye on," or "Your water looks healthy." Each result is a card with How to fix advice. Because the Tank Builder knows your fish, it also checks whether your pH and temperature suit them. See Water test results explained.

The grading happens whether or not you log the reading; logging just saves the numbers.

Common problems

I don't see a log button. Sign in. Signed out, the tab only shows a Sign in link.

The log button is grayed out. Enter at least one value. It's also briefly disabled while a save is in progress.

I tapped Save tank & log reading and nothing happened. You're probably at the 4 tank limit. Scroll up to the save section to see the message. Load one of Your tanks and log to it instead, or delete a tank to make room.

I logged the same reading twice. Your values stay in the boxes after logging, so tapping again logs a duplicate. Delete the extra with the trash icon.

My old readings are missing. Only the latest 20 per tank show. Make sure you've loaded the right tank. Use Download my data on Account & data to see all of them.

My reading shows the wrong time. Readings are stamped when you tap Log reading, in your device's time zone. They can't be backdated; add the real test time in the note.

I see "Couldn't log the reading. Please try again." A connection or server problem. Check your connection and tap Log reading again. If it keeps failing, email support@undergroundaquarium.com.

Readings from one tank don't show on another. Each saved tank keeps its own history. Load the tank you logged to.