# ACV Viper vs ReefATLAS PAR Estimator

The clearest difference is in-app purchases: ACV Viper at none against ReefATLAS PAR Estimator's 1. ReefATLAS PAR Estimator's advantage is update cadence (daily vs fortnightly) and iOS requirement (14.0 vs 17.0). On price, ads and device support there is nothing between them.

Both are free to download. ReefATLAS PAR Estimator sells 1 in-app purchase, starting at $4.99 per month. ACV Viper asks for nothing beyond the download.

ACV Viper ships an update fortnightly, ReefATLAS PAR Estimator daily. The most recent releases landed on October 16, 2026 and October 19, 2026 respectively.

## The numbers

| Metric | ACV Viper | ReefATLAS PAR Estimator |
| --- | --- | --- |
| Price | Free | Free |
| Rating | — | **[5.0 (1 ratings)](https://appshunter.io/ios/app/reefatlas-par-estimator/id6777574663/reviews)** |
| Number of ratings | — | **1** |
| In-app purchases | **No** | Yes |
| Ads | No | No |
| Update frequency | Fortnightly | **Daily** |
| Monetization | — | Subscription |
| Size | 190 MB | 27 MB |
| Requires iOS | 17.0 | **14.0** |
| Devices | iPhone, iPad | **iPhone, iPad, iPod** |
| Age rating | 4+ | 4+ |
| Developer | [ACV Auctions Inc](https://appshunter.io/developer/969808942) | [JONATHAN ALBERT PITTMAN](https://appshunter.io/developer/6777574665) |

## What reviewers say

### ACV Viper

[App page](https://appshunter.io/ios/app/acv-viper/id6476239640)

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

**In-app purchases:** none


### ReefATLAS PAR Estimator

[App page](https://appshunter.io/ios/app/reefatlas-par-estimator/id6777574663)

This app helps reef aquarium enthusiasts estimate and visualize light distribution without a PAR meter. It allows users to input tank dimensions, lighting equipment, and water conditions to predict PAR levels and make informed decisions about coral placement and lighting setups. The tool offers interactive 3D visualizations and supports a wide range of popular reef lighting systems.

**Highlights:** Interactive 3D PAR heatmap visualization, Support for popular reef aquarium lighting systems, Multi-fixture light array setup, Fixture placement and angle controls, Spectrum and intensity adjustment tools, Custom tank dimension configuration, Surface agitation and lid modeling

**Features:** macOS Compatibility

**In-app purchases (1)**

| Purchase | Price | Billing |
| --- | --- | --- |
| ReefATLAS PAR Estimator Monthly | $4.99 | per month |


## Frequently asked questions

### Is ACV Viper free?

ACV Viper is free to download, with no in-app purchases.

### Is ReefATLAS PAR Estimator free?

ReefATLAS PAR Estimator is free to download, with in-app purchases available.

### Do ACV Viper or ReefATLAS PAR Estimator have ads?

Neither ACV Viper nor ReefATLAS PAR Estimator shows ads.

### Which is updated more often, ACV Viper or ReefATLAS PAR Estimator?

ACV Viper ships an update fortnightly, and ReefATLAS PAR Estimator daily. Most recently, ACV Viper was updated on October 16, 2026 and ReefATLAS PAR Estimator on October 19, 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.*