# Z21 vs EHEIM Digital Connect

The clearest difference is rating: Z21 at 3.8 against EHEIM Digital Connect's 1.7. Z21 also leads on review sentiment (38% vs 15%). EHEIM Digital Connect's advantage is in-app purchases (none vs 1). On price, ratings volume, update cadence and ads there is nothing between them.

Both are free to download. Z21 sells 1 one-off in-app purchase. EHEIM Digital Connect asks for nothing beyond the download.

Z21 holds the better App Store score, 3.8 against 1.7. Both are backed by a comparable volume of ratings — 13 and 12 respectively. Written reviews point the same way: 38% of Z21's written reviews are positive against 15% of EHEIM Digital Connect's.

Z21 ships an update every 3 weeks, EHEIM Digital Connect every 5 weeks. The most recent releases landed on October 6, 2026 and October 15, 2026 respectively.

## The numbers

| Metric | Z21 | EHEIM Digital Connect |
| --- | --- | --- |
| Price | Free | Free |
| Rating | **[3.8 (13 ratings)](https://appshunter.io/ios/app/z21/id1114706450/reviews)** | [1.7 (12 ratings)](https://appshunter.io/ios/app/eheim-digital-connect/id6501949799/reviews) |
| Number of ratings | **13** | 12 |
| Positive reviews | **38.3% of reviews** | 14.8% of reviews |
| In-app purchases | Yes | **No** |
| Ads | No | No |
| Update frequency | **Every 3 weeks** | Every 5 weeks |
| Monetization | Free with in-app purchases | **Free** |
| Size | 232 MB | 47 MB |
| Requires iOS | **12.0** | 13.0 |
| Devices | **iPhone, iPad, iPod** | iPhone, iPod |
| Age rating | 4+ | 4+ |
| Developer | [Modelleisenbahn GmbH](https://appshunter.io/developer/533805542) | [Eheim GmbH & Co. KG](https://appshunter.io/developer/888209218) |

## What reviewers say

### Z21

[App page](https://appshunter.io/ios/app/z21/id1114706450)

Control your model train layout and locomotives wirelessly from your iOS device. Manage your locomotive library, program digital components, and operate switches and signals with an intuitive touch interface. Enjoy a realistic train control experience with customizable driver cabs.

**Highlights:** Wireless control of locomotives and layout, Manage locomotive library with images, Program digital components, Intuitive graphic interface for switches and signals, Downloadable driver cabs for realistic control, Demo mode available

**Features:** Family Sharing

**In-app purchases (1)**

| Purchase | Price | Billing |
| --- | --- | --- |
| Z21 Full Version | $17.99 | one-time |

**What reviewers like**

- 👍 Intuitive and user-friendly interface
- 🚀 Fast and reliable locomotive control
- 💡 Innovative layout design with schematic control station
- 🎨 Clean, modern orange and black design
- 📱 Works seamlessly across multiple iOS devices

**What reviewers complain about**

- 🐛 Frequent app crashes and freezes
- 🔌 Connection drops to Z21 control station
- ⚠️ White screen startup issues in recent updates
- 🎮 Throttle display bugs showing incorrect speeds
- 📉 Slow performance on older devices

**Reported bugs**

- App crashes on startup (white screen issue)
- Connection drops to Z21 central station
- Throttle display shows incorrect or blank speeds
- Function buttons not responding properly in multitraction mode
- Route synchronization failures across multiple control station pages

**Requested features**

- Offline locomotive database access
- Dark mode or customizable color schemes
- Background image support for layout design
- Turntable/rotary module support
- Automatic event-based control (occupancy detection, crossing automation)


### EHEIM Digital Connect

[App page](https://appshunter.io/ios/app/eheim-digital-connect/id6501949799)

This app allows you to connect, set up, and manage various EHEIM digital aquarium devices from your smartphone or tablet. Customize settings for optimal results and ensure your devices are always up-to-date for a thriving aquatic environment.

**Highlights:** Connect and manage digital aquarium devices, Customize device settings, Update device firmware, Control filters, lighting, heaters, and more, Monitor aquarium components

**Features:** macOS Compatibility, Vision Pro support

**In-app purchases:** none


## Frequently asked questions

### Is Z21 free?

Z21 is free to download, with in-app purchases available.

### Is EHEIM Digital Connect free?

EHEIM Digital Connect is free to download, with no in-app purchases.

### Which has better reviews, Z21 or EHEIM Digital Connect?

Z21 is rated higher. Z21 averages 3.8 out of 5 from 13 ratings, while EHEIM Digital Connect averages 1.7 from 12 ratings.

### Do Z21 or EHEIM Digital Connect have ads?

Neither Z21 nor EHEIM Digital Connect shows ads.

### Which is updated more often, Z21 or EHEIM Digital Connect?

Z21 ships an update every 3 weeks, and EHEIM Digital Connect every 5 weeks. Most recently, Z21 was updated on October 6, 2026 and EHEIM Digital Connect on October 15, 2026.

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*Compared by [AppsHunter](https://appshunter.io/) from daily US App Store data. Review summaries are generated from verbatim App Store reviews.*