# ISD Link vs HydroponicsCalc

The clearest difference is price: ISD Link at Free against HydroponicsCalc's $1.99. ISD Link also leads on update cadence (every 3 weeks vs every 4 months) and ratings volume (23 vs 1). HydroponicsCalc's advantage is rating (5.0 vs 2.1). On ads and in-app purchases there is nothing between them.

ISD Link is free to download; HydroponicsCalc costs $1.99 up front. Neither carries in-app purchases, so what you see is what you pay.

HydroponicsCalc holds the better App Store score, 5.0 against 2.1. That said, the two scores are not equally well evidenced: ISD Link has 23 ratings behind it against 1, so its average is the more settled of the two.

ISD Link ships an update every 3 weeks, HydroponicsCalc every 4 months. The most recent releases landed on October 20, 2026 and October 23, 2026 respectively.

## The numbers

| Metric | ISD Link | HydroponicsCalc |
| --- | --- | --- |
| Price | **Free** | $1.99 |
| Rating | [2.1 (23 ratings)](https://appshunter.io/ios/app/isd-link/id1568620244/reviews) | **[5.0 (1 ratings)](https://appshunter.io/ios/app/hydroponicscalc/id6775172331/reviews)** |
| Number of ratings | **23** | 1 |
| Positive reviews | 21.0% of reviews | — |
| In-app purchases | No | No |
| Ads | No | No |
| Update frequency | **Every 3 weeks** | Every 4 months |
| Monetization | **Free** | Paid |
| Size | 61 MB | 3 MB |
| Requires iOS | **13.0** | 17.0 |
| Devices | **iPhone, iPad, iPod, Apple Watch** | iPhone, iPad |
| Age rating | 4+ | 4+ |
| Developer | [深圳艾斯特创新科技有限公司](https://appshunter.io/developer/1405370693) | [Douglas Stieber](https://appshunter.io/developer/6771586128) |

## What reviewers say

### ISD Link

[App page](https://appshunter.io/ios/app/isd-link/id1568620244)

This app allows interaction with various smart devices. It prioritizes user privacy by saving all data locally and not collecting personal information. Bluetooth is required for device scanning and connection.

**Highlights:** Smart device interaction, Local data saving, No account registration, Bluetooth connectivity, Supports numerous device models

**Features:** macOS Compatibility

**In-app purchases:** none


### HydroponicsCalc

[App page](https://appshunter.io/ios/app/hydroponicscalc/id6775172331)

Manage your hydroponic garden with this comprehensive tool. Track reservoir levels, mix nutrients precisely, calculate pH and VPD, and document your grow with a journal and harvest log. Supports both US and metric units.

**Highlights:** Reservoir management dashboard, Concentrate and EC mixing calculators, pH and VPD calculators, Grow journal with photo timeline, Harvest log and ROI dashboard, Light schedule tracker, US & Metric unit support

**Features:** macOS Compatibility

**In-app purchases:** none


## Frequently asked questions

### Is ISD Link free?

ISD Link is free to download, with no in-app purchases.

### Is HydroponicsCalc free?

HydroponicsCalc costs $1.99, with no in-app purchases.

### Which has better reviews, ISD Link or HydroponicsCalc?

HydroponicsCalc is rated higher. ISD Link averages 2.1 out of 5 from 23 ratings, while HydroponicsCalc averages 5.0 from 1 ratings.

### Do ISD Link or HydroponicsCalc have ads?

Neither ISD Link nor HydroponicsCalc shows ads.

### Which is updated more often, ISD Link or HydroponicsCalc?

ISD Link ships an update every 3 weeks, and HydroponicsCalc every 4 months. Most recently, ISD Link was updated on October 20, 2026 and HydroponicsCalc on October 23, 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.*