Comparison

Secchi vs HydroCrowd

Price, ratings, monetisation and update history for both apps, side by side β€” with what reviewers say about each.

Head to head
About

Secchi

Features
Read full description

Climate change is threatening the phytoplankton that underpins the marine food chain. We must understand why before it's too late. Secchi enables you to take part in the Secchi Disk citizen science study and help collect essential data on the phytoplankton.

About

HydroCrowd

Features
Read full description

HydroCrowd is a research project of the Justus Liebig University Giessen, which investigates the potential of participatory monitoring to increase the availability of hydro-climatic data for sustainable water management, especially in remote areas in the global south. The project will test different approaches to engage volunteers through the implementation and evaluation of a participatory hydro-climatic monitoring program in selected mountain regions in Ecuador, Honduras and Tanzania. Furthermore, it will demonstrate how the data collected by the volunteers can be used in hydrological modelling and, therefore, improve the prediction of climate change impact on water resources in data-scarce regions. The project outputs can be used to guide the development of future participatory monitoring programs and stimulate upscaling of the approach to other regions to address the lack of hydro-climatic data for evidence-based decision making and sustainable water management. Volunteers participate by reporting measurements from easy-to-use instruments at weather and water stations installed in the project areas in Ecuador, Honduras and Tanzania. These measurements include rainfall, air temperature and humidity, as well as the water level and turbidity of rivers and streams. To evaluate the quality of the data, the data will be compared with automated reference measurements at selected sites. These are then systematically examined and tested for their suitability for modeling. This app enables easy submission of data by the volunteers and provides instructions on how to collect data. Furthermore, users can view the data previously submitted by other volunteers. As the remote study areas have limited network access, it is recommended to download the map of your region and the locations of the stations before going to any of the HydroCrowd stations. In addition to reporting measurements from the HydroCrowd stations, volunteers also have the opportunity to create spots to record their own rainfall data, and to report weather events using β€˜photo notes’. The HydroCrowd Citizen Science App is running on the SPOTTERON Platform.

Screenshots

Secchi4 screens
HydroCrowd4 screens

Verdict

The call

The clearest difference is update cadence: HydroCrowd at every 3 months against Secchi's every 7 months. HydroCrowd also leads on iOS requirement (12.0 vs 15.6). On price, ads, in-app purchases and device support there is nothing between them.

Scored on Price Β· Rating Β· Positive reviews Β· Number of ratings Β· Update frequency Β· Ads Β· In-app purchases Β· Monetization Β· Best chart rank Β· Devices Β· Requires iOS

CostPrice Β· In-app purchases Β· Ads Β· Monetization

Both are free to download. Neither carries in-app purchases, so what you see is what you pay.

UpkeepUpdate frequency

Secchi ships an update every 7 months, HydroCrowd every 3 months. The most recent releases landed on September 23, 2026 and September 10, 2026 respectively.

Scorecard2 real differences Β· 4 level
Secchi versus HydroCrowd: the parameters behind the verdict, then further details
ParameterSecchiHydroCrowd
PriceFreeFree
Update frequencyEvery 7 monthsEvery 3 months β€” better
AdsNoNo
In-app purchasesNoNo
DevicesiPhone, iPad, iPodiPhone, iPad, iPod
Requires iOS15.612.0 β€” better
Further details β€” not scored
Size45 MB61 MB
Age rating4+4+
DeveloperThe Secchi Disk FoundationSPOTTERON Gmbh

In-app purchases

None

Secchi

No in-app purchases

None

HydroCrowd

No in-app purchases

Questions

Is Secchi free?
Secchi is free to download, with no in-app purchases.
Is HydroCrowd free?
HydroCrowd is free to download, with no in-app purchases.
Do Secchi or HydroCrowd have ads?
Neither Secchi nor HydroCrowd shows ads.
Which is updated more often, Secchi or HydroCrowd?
Secchi ships an update every 7 months, and HydroCrowd every 3 months. Most recently, Secchi was updated on September 23, 2026 and HydroCrowd on September 10, 2026.

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