Read and write NFC tags to automate your aquarium's temperature and light

If you have an aquarium at home, you've probably noticed that control the light, temperature and other equipment It can be a real hassle if you do everything manually. Turning lights on and off, activating heaters, operating recirculation pumps… in the end, it's a lot of small, repetitive tasks that take up time, and if you forget something one day, your fish and plants might notice.

The good news is that today we can take advantage of the NFC technology combined with home automation (for example, with Home Assistant) so that a simple sticker or card allows us to launch complex automations: from adjusting the aquarium lighting to changing the temperature or activating a night mode, all by bringing the mobile phone close to a label.

What is NFC and why is it perfect for your aquarium?

NFC (Near Field Communication) technology allows very short range wireless communication between devicesIt's the same one you use when you pay with your mobile phone at a card reader or when you share data with another device by bringing them a few centimeters close together.

In home automation, and particularly in aquariums, the NFC tags (cards or stickers) They become a kind of wireless and battery-free "physical buttons": you stick them wherever you want (for example, on the aquarium cabinet) and, when read with your mobile phone, they launch the automation that you have configured in your system, such as Home Assistant.

What's truly interesting is that the NFC tag doesn't store all the automation, but rather a unique identifier that your home automation system recognizesThus, a single sticker can trigger complex actions: changing the water heater temperature, modifying the light level, activating a maintenance mode, or turning on water recirculation after a partial change.

Furthermore, NFC tags do not require a power source: They are powered by the energy of the mobile phone's own NFC field.This means they can last for years stuck to the glass, the furniture, the side of the filter, or wherever is most convenient for you, without you having to worry about batteries or cables.

Basic requirements for using NFC tags in home automation and aquariums

Before you start sticking labels on like there's no tomorrow, it's important to be clear What exactly do you need to make everything work?, both at the hardware and software level.

Required hardware

First, you need to have blank NFC tags and an NFC-compatible deviceWithout these two pieces, there's not much that can be done.

• Rewritable NFC tags or stickers: There are countless models on the market (rigid cards, round, square, colored stickers, waterproof ones, etc.). For home automation with Home Assistant and aquarium use, ideally they should be reprogrammableso that you can change the automation if you make a mistake or if you want to use them for something else in the future.
• Smartphone with NFC: Most recent mobile phones include it. On iPhones, from the iPhone 7 onwards; on Android, practically any mid-range or high-end model since 2015 usually includes NFC, although it's advisable Check the technical specifications of your model just in case.

If for whatever reason your phone doesn't have NFC, you still have the option of using a external NFC reader/writer connected to a computerAlthough for practical home automation, the usual thing is to use a smartphone, which is what we always have on hand next to the aquarium.

Recommended applications for programming NFC tags

Once the hardware is sorted, it's time to choose the application that you will use to read and write the NFC tagHere are two different scenarios: generic NFC use (for URLs, text, etc.) and specific use with Home Assistant.

• NFC Tools: It's a very popular app on Android and iOS for reading, writing, and managing NFC tags. It allows you to save URLs, text, emails, phone numbers, WiFi or Bluetooth settings and much more. It's ideal if you want to use some NFC tags generically (for example, to open a webpage with aquarium controller settings, information on your fish, etc.).
• NFC TagWriter: focused on making it easy to write records to tags. If you just want add simple data and manage a small batch of labelsIt's a quick and easy option.
• Specific managers (NFC Manager and similar): useful when working with many NFC tags and you need extra organizational featuresThey can work well if you fill the house with tags for different home automation scenarios, not just the aquarium.

To integrate these labels into automations such as “scan = home automation action”, the key role is played by the official Home Assistant appwhich is responsible for associating each tag with a specific trigger within your system.

Use NFC with Home Assistant to automate your aquarium

Home Assistant is one of the most flexible home automation systems, and among its many functions it allows use NFC tags as triggersNot only does it let you create buttons and controls in the web interface, but you can also launch automations by bringing your mobile phone close to an NFC sticker.

For this to work, it is essential that Use the official Home Assistant app on your smartphoneFrom a web browser you can create labels at a logical level (in the database), but the physical writing on the NFC sticker has to be done from the mobile app.

There is an important security detail: your mobile operating system requires that Make sure your phone is unlocked to read NFC tags in the backgroundThis feature has been available on iOS since version 14 and on Android since version 10. This prevents the phone from performing sensitive actions without your knowledge, which is crucial if you're managing things like home access, heaters, lighting, etc.

Once configured, You can use the labels even when you're not at homeThe only essential requirement is that the Home Assistant app has remote access to your serverIt can be via VPN, a Cloudflare Tunnel, a reverse proxy (Nginx Proxy Manager, Traefik…) or any other solution that allows you to enter with a domain and HTTPS.

How to create and write NFC tags in Home Assistant

The process within Home Assistant is quite straightforward. The general flow consists of: create the logic tag within the system, burn it onto an NFC sticker, and then use it as a trigger in an automation.

Creating the label from the app

From the Home Assistant mobile app, the first thing to do is enter the side menu and access the section “Settings > Tags”There you will see a list of all the tags you have already registered, along with useful information such as whether they have been physically written to an NFC sticker and when they were last executed.

To create a new one, click on “Add tag”You will be asked to give it a descriptive name (for example, “Aquarium Night Mode” or “Change Light to Cool White”) and, if you wish, you can define a Custom tag IDIf you leave it blank, Home Assistant will generate one automatically.

When you've finished filling in these fields, tap on “Create and write”At that point, the app will ask you to bring the NFC sticker or card close to the back of your phone. After one or two seconds, if everything goes well, you'll see a message indicating that the label has been written correctly and it will be ready to use as a trigger.

Configure NFC-triggered automations

A freshly written label doesn't do anything on its own yet: it simply contains the identifierThe next step is to tell Home Assistant which automation should run when that tag is scanned.

To do this, from the app or the web interface, go to “Settings > Automations and scenes”, click on “Create automation” and, in the “When” (or “Trigger”) section, choose the type of trigger "Hashtag"You will see a list of all the NFC tags you have created; select the one you want to associate with that automation.

Next, you can define the conditions and actionsFor example, you can program the tag to only activate at night or if the aquarium temperature falls below a certain value. In the "Then do" section, you choose what should happen: turn on a light, change its intensity, adjust the temperature, activate a relay, start a recirculation mode, etc.

It is important to understand that, although an automation has dozens of different actionsThe NFC tag only stores the identifier. This gives you enormous freedom: you can have a sticker on the aquarium cabinet that, when scanned, changes the lighting, activates the heater, adjusts the recirculation, and sends a notification to your mobile phone with the current water parameters, all in one go.

Examples of using NFC tags in your aquarium

The most typical example of using NFC and Home Assistant is something like open the garage, turn on lights, or activate a “shower mode” in the bathroom. But if we bring all this down to the world of aquariums, the possibilities are just as powerful.

Imagine you place an NFC sticker right next to the aquarium to activate “night mode”When you bring your mobile phone close: the aquarium lights dim, the lighting changes to warmer or lunar tones, the intensity of some pumps is reduced, and perhaps the living room blinds are lowered slightly if you also have them integrated.

Another tag might be next to the maintenance kit. Scanning it would reveal activate a “water change” modeCertain pumps are turned off, the heater is adjusted to prevent spikes, a brighter auxiliary light is turned on so you can see what you're doing better, and once the process is complete, another label restores the aquarium's normal settings.

You can also use an NFC tag attached to the side of the furniture to Turn on only the work lights for a few minutes (for example, to prepare food or check something) and then turn off automatically. Or a tag on your mobile phone or a card that you always have with you to activate a "vacation mode" with light and temperature settings adjusted for long absences.

If you have several aquariums at home, NFC tags help you to differentiate specific actions for each one: a label on each piece of furniture that adjusts the specific parameters of the corresponding aquarium, without having to search in the app which light or which smart plug corresponds to each tank.

Program NFC tags step by step with NFC Tools

Beyond Home Assistant, you might want Use your NFC tags for other aquarium-related functionsOpen a spreadsheet with water parameter logs, a maintenance schedule document, or a fact sheet for each fish species. For this, NFC Tools is your best friend.

Requirements for writing an NFC tag with NFC Tools

To start programming NFC tags generically with NFC Tools, you only need a blank sticker, a compatible smartphone, and the installed app.

1. Blank NFC tag: They require no prior data and are reprogrammable. They are easy to find and usually cost between €0,20 and €0,30 per unit if you buy packs.
2. NFC-enabled device: An Android phone or an iPhone 7 or later. Make sure your model supports reading and writing tags.
3. NFC Tools application: Available for free on Google Play and the App Store. It's one of the most complete and user-friendly tools for this type of task.
4. NFC activated on the mobile: Go into Settings and confirm that the NFC function is turned on before you start writing the label.

Mobile device preparation

Before writing anything on the label, make sure the phone is properly prepared to work with NFCA quick review of the settings will save you from many reading errors.

• On Android, go to “Settings > Connections” (or similar) and activate NFC. Depending on the customization layer, the option may be in another menu, but it is usually easy to find if you search for “NFC” in the settings search box.
• On iPhone, starting with the 7 and with iOS 13 or higher, NFC reading is enabled by default.However, to write labels you will need to use NFC Tools or another specific app.
• Keep the updated operating systemThe latest versions usually improve NFC compatibility and the stability of the apps that use it.

Writing an NFC tag with iPhone

If you use an iPhone, the process for writing a tag with NFC Tools is quite simple and straightforward, but it's worth following the steps. the correct order to avoid mistakes.

1. Make sure you have a iPhone 7 or later with iOS 13 or later.
2. Download and install the app NFCTools from the App Store.
3. Open NFC Tools and go to the tab "Write".
4. Toca “Add a record” and choose the type of content you want to save: URL, text, email, phone number, etc.
5. Configure that record with the information you want (for example, the URL of your aquarium controller's web panel) and press "Validate".
6. Tap the option “Write / X bytes” to start recording.
7. Bring your iPhone close to the NFC tag until the app indicates that it is ready. writing has been successfully completed.

Writing an NFC tag with Android

On Android, the workflow is practically the same. The good thing is that, on many models, the Automatic label reading is immediate, without doing anything more than bringing the mobile phone closer.

1. Install the app NFCTools from Google Play.
2. Open it and go to the tab "Write".
3. Tap on “Add a record” and select the type of action or content.
4. Fill in the required information and validate the registration.
5. Balance “Write / X bytes” to start recording.
6. Bring your phone close to the NFC tag and wait for the app to confirm that It has been recorded correctly.

Writing with NFC reader/writer on computer

If you prefer to work from your PC, or your mobile phone doesn't have NFC, you can use a compatible USB reader/writer and desktop software.

1. Purchase a compatible NFC reader/writer Windows, macOS, or Linux.
2. Install a suitable program, such as TagXplorer or NFC Tools for desktop.
3. Connect the reader to the computer via USB.
4. Open the software and follow the wizard to write on the label.
5. When prompted, place the NFC tag over the reader and wait for it to... complete the programming.

Types of content you can store on an NFC tag

Depending on the app you use (NFC Tools, TagWriter, etc.), you can store different types of information on your NFC tagsSome of the most common ones will be especially useful for your aquarium.

• URL: perfect for opening directly web interface of your aquarium controller, a page with the data sheet for each fish or an online document with the record of parameters.
• Text: useful for showing quick notes or maintenance instructions: frequency of water changes, fertilizer dosages, filter cleaning reminders, etc.
• Links to apps: For example, launching a WhatsApp message with a predefined message to notify the family group that You have already fed the fish or open a specific app for your home automation system.
• Cashless systems: Although they are used more in events and cashless payments, the technology is the same as that of your NFC tags for home automation.
• Device settings: Activating WiFi or Bluetooth, opening certain mobile settings... It's not the most typical thing in aquariums, but it can be useful if you usually connect your mobile to a controller via Bluetooth.

In all cases, the app will show how many bytes the information you are going to record occupiesThis is useful information because NFC tags have limited capacity, and depending on what you store (especially if it's long text) you can get close to the maximum.

How to read NFC tags: differences between Android and iPhone

Reading an NFC tag is much simpler than programming it: in most cases, all you need to do is bring the mobile phone close to the sticker or card and wait a second. Even so, there are nuances between Android and iOS that are worth taking into account.

NFC reading on Android

On Android, once you have NFC enabled in mobile settingsSimply place the back of your phone on the sticker. The exact position of the internal reader varies depending on the model (sometimes it's higher, sometimes more centered), so you might have to "find the right spot."

• Go to Settings and activate NFC in the connections/networks section.
• Bring your mobile device close to the NFC tag. If the tag contains a URL, text, or a standard action, the system will display a notification or pop-up window with the content.
• For more advanced uses (Home Assistant automations, reading specific fields, etc.) you may need have the corresponding app open or that it runs in the background.

In general, screen reading on Android is very fast. However, keep in mind that if you use metal or very thick cases, it might be slower. cause interference and hinder readingRemove the case if you have persistent problems.

NFC reading on iPhone

On iPhone, the experience is also quite smooth, especially since iOS 13. Starting with the iPhone 7, You can read NFC tags without additional apps. for basic content such as URLs or text, and the system works similarly to Android.

• Check your iOS model and version. They support background NFC reading..
• Bring the top of your iPhone close to the NFC tag: the reader is usually in the camera area.
• For cases like label writing or home automation automationsYou will need to use the appropriate app (NFC Tools, Home Assistant, etc.).

Customizing actions when reading NFC tags on iPhone is somewhat more limited than on many Android devices, but for Home Assistant integrations the experience is still very good as long as you use the official app and have access to the server.

Common problems with NFC tags and how to fix them

Even if everything is set up correctly, it's normal for an issue to appear from time to time. Error reading or writing an NFC tagThey almost always have an easy solution if you know where to look.

One of the curious cases is when the Home Assistant app displays a read errorHowever, the automation still runs. This is usually due to minor delays or occasional communication issues with the server. If you see that the action has been performed (for example, the aquarium light has changed), you can rest assured.

If your phone doesn't detect the tag, check the basics: that NFC must be enabled, and the phone must be unlocked. And make sure there isn't a metal case blocking the signal. Also, try slightly moving the phone's position, because each model has the NFC reader in a different spot.

When reading is intermittent or slow, it is advisable to identify correctly. Where is the reader on your smartphone? and get used to positioning that exact area close to the label. Sometimes we think it's not working, but it's just a matter of millimeters of difference.

Another classic problem is trying to read two or more NFC stickers stuck togetherIn that case, the mobile device might capture multiple tags simultaneously, leading to errors or unexpected results. To avoid this, always leave some space between tags, especially if each one triggers different automations.

Advantages and disadvantages of NFC tags in home automation and aquariums

NFC tags are a powerful tool for simplify repetitive tasks and make your aquarium "smarter"But they also have their limitations. It's a good idea to know both sides of the coin before filling your house with stickers.

main advantages

• Easy to use: Bringing your phone close to a sticker is as easy as paying with your phone. Once set up, NFC tags are faster than opening an app and searching for the right button for each action.
• No energy required: The labels don't require batteries; they are powered by the mobile phone's NFC field. They can remain attached to the aquarium cabinet for years without losing functionality, which makes them very reliable and low maintenance.
• Reasonable security: For an NFC tag to trigger an automation in Home Assistant, the mobile device must be unlocked and have access to the serverA label by itself, without that access, is useless.

Disadvantages and limitations

• Very short range: you should bring the phone very close to the label, sometimes even "finding the exact spot" of the reader. For some people, this can be somewhat inconvenient compared to other systems (such as physical buttons or voice control).
• Possible physical manipulation: If the stickers are accessible, someone can tear them off, move them, or even replace them. From a security standpoint, the information they contain is usually not critical (an ID), but practically speaking, it can be problematic. to cause certain automations to stop working.
• Interferences and sheaths: Metal lids, thick covers, or the presence of several labels together can cause erratic or failed readingsYou have to be a little careful about where you stick each label and what kind of case you use.

However, NFC tags remain very cheap and extremely useful For home automation and aquariums. With a small investment and a little time setting them up, you gain speed, convenience, and reduce many everyday oversights.

Integrating NFC tags with Home Assistant and apps like NFC Tools becomes a very practical way to keep the temperature, lighting, and operating modes of your aquarium Simply bring your phone close to a sticker. Properly placed and configured, they allow you to activate night or maintenance modes, open control panels, record parameters, or launch complex automations—all at minimal cost and without complicating things every time you want to make an adjustment.