Privacy Policy

The short version

The calculators on reefcalcs run in your browser — your calculator inputs are not sent to us. There are no accounts to sign up for right now; the whole site works without one. We do not sell your data. We use Google Analytics 4 and Vercel Analytics to understand which pages get visited. The site carries Amazon affiliate links and is set up for Google AdSense; both are governed by their own privacy policies and disclosed below.

Calculations run in your browser

Every calculator on reefcalcs is a client-side JavaScript function. Your tank dimensions, dosing inputs, water parameters, and results are computed locally in your browser and are not transmitted to our servers as part of running a calculation. No tank data reaches our server.

Accounts (not currently offered)

Account sign-up is not open. The code for optional accounts exists, and if we switch it on, this section describes what would be stored, in a database hosted on Neon, and this page's date will move:

• Your email address — used to sign in, verify your account, and send password resets.
• A hash of your password — never the plaintext password. Passwords are hashed with bcrypt before storage; we cannot read or recover your original password.
• Your username — optional, only used if you choose to make a tank public.
• Tank data you choose to save — name, dimensions, target parameters, dosing schedule, and equipment list.
• Parameter logs — the test readings you record for a saved tank.

Transactional emails (verification, password reset, welcome) would be sent via Resend. There is no newsletter or digest email.

Analytics

We use Google Analytics 4 (measurement ID G-Y2C399QSF1) and Vercel Analytics. GA4 is described under Cookies and in the consent section below. Vercel Analytics records anonymized aggregate page views. It records the page URL, referring URL, country (derived from IP at request time, then discarded), device type, and browser/OS family. Vercel Analytics does not use cookies and does not store your IP address. See Vercel's analytics privacy policy for the full technical detail.

We also send two custom GA4 events when an affiliate product block is shown or clicked (which product, which placement on the page). They contain no personal data.

Affiliate links

Some outbound links on reefcalcs may be affiliate links — most commonly via the Amazon Associates program. If you click an affiliate link and make a purchase, reefcalcs may earn a commission at no additional cost to you. Affiliate links never change what a calculator outputs, what a parameter range is, or which product a comparison page recommends. The math and the cited sources come first.

As an Amazon Associate, reefcalcs may earn from qualifying purchases.

Third-party advertising (Google AdSense)

reefcalcs is set up for Google AdSense: the AdSense script loads on every page, although ad units are not switched on yet. Once they are, Google and its advertising partners may set cookies, use device identifiers (including the advertising ID on mobile devices), and collect information about your visits to this site and other sites in order to provide advertisements about goods and services that may interest you. This activity is governed by Google's privacy policy, not ours.

Specifically:

• Third-party vendors, including Google, use cookies to serve ads based on your prior visits to this website or other websites.
• Google's use of advertising cookies enables it and its partners to serve ads to you based on your visit to reefcalcs and/or other sites on the internet.
• You can opt out of personalized advertising by visiting Google Ads Settings. You can also opt out of a third-party vendor's use of cookies for personalized advertising by visiting aboutads.info.
• For more on how Google uses information from sites or apps that use its services, see policies.google.com/technologies/partner-sites and policies.google.com/technologies/ads.

Cookies and similar technologies

reefcalcs does not set first-party tracking cookies. Since accounts are not open, we set no first-party cookies. (If accounts open, signing in would set one strictly-necessary, HTTP-only session cookie.)

Third parties may set cookies through this site:

• Google AdSense may set advertising cookies (including the DoubleClick IDE and ANID cookies) to measure and serve ads.
• Google Analytics 4 (GA4) sets the _ga and _ga_<measurement_id> cookies to count unique visitors and measure how pages are used. IP addresses are anonymised before storage. We use the data to see which calculators are popular and which pages need improvement — not to profile individual users.
• Amazon may set cookies when you click an affiliate link and arrive on amazon.com.

Most browsers let you block or delete cookies in their settings. Blocking advertising cookies will not break the calculators on this site; it will only result in less relevant ads being shown to you.

Visitors from the EEA, UK, and Switzerland

If you are visiting from the European Economic Area, the United Kingdom, or Switzerland, a consent banner is shown on your first visit once Google's consent message is active for this site. The banner is provided by Google's certified Consent Management Platform (CMP) and complies with the IAB Europe Transparency & Consent Framework (TCF) v2 and the EU's Digital Markets Act (DMA) requirements for sites running Google AdSense.

The banner asks whether you consent to:

• Personalized advertising (using cookies and identifiers to tailor ads to you).
• Ad and content measurement, audience research, and product development by Google and its advertising partners.

You can choose Consent, Do not consent, or use Manage options to make granular choices per vendor and per purpose. Your choice is recorded by the CMP and applies on subsequent visits until you clear cookies or change your choice. To change your choice later, you can re-open the consent banner from the “Manage cookie preferences” control that the CMP exposes, or clear cookies for reefcalcs.com in your browser.

The CMP also controls Google Analytics 4. We use Google's Consent Mode v2 with all four signals (ad_storage, ad_user_data, ad_personalization, analytics_storage) set to “denied” by default for visitors in these regions. Elsewhere, the three advertising signals default to “denied” and analytics_storage defaults to “granted”, so GA4 sets its cookies without a banner. If you consent, GA4 sets cookies and reports your session to us in aggregated form. If you do not consent, GA4 still reports a small set of cookieless pings (the “modeled” conversions feature) which contain no identifiers and cannot be used to track you across sites.

If you choose “Do not consent,” non-personalized ads may still be shown. Non-personalized ads use contextual signals (such as the topic of the current page) rather than your past activity, and they are permitted under GDPR without consent.

The legal basis we rely on for processing personal data via the ad network in these regions is your consent (GDPR Article 6(1)(a)). You can withdraw consent at any time, and doing so does not affect the lawfulness of processing carried out before withdrawal.

California residents (CCPA / CPRA)

reefcalcs does not sell personal information for money. Under the CCPA/CPRA, the term “sell” and “share” can include the disclosure of identifiers (including online identifiers and cookie IDs) to advertising partners for cross-context behavioral advertising. To the extent that the use of Google AdSense on this site constitutes “sharing” under the CPRA, California residents have the right to opt out. You can do so by visiting Google Ads Settings to opt out of personalized advertising.

What we don't do

• No account is required to use anything on the site.
• We don't collect your calculator inputs; the math runs in your browser.
• No selling, sharing, or licensing of personal data we collect to third parties for their own marketing.

Email

If you email hello@reefcalcs.com, that message is delivered to the operator via Cloudflare Email Routing. The contents of the email are subject to whatever email provider you used to send it and whatever provider the operator uses to receive it. We will never sign you up for anything based on emailing in.

Third-party services we use

• Vercel — hosts the site and runs analytics. See their privacy policy.
• Neon — would host account data (email, password hash, saved tanks, parameter logs) if accounts open; nothing is stored there today. See their privacy policy.
• Resend — would send transactional account email (verification, password reset, welcome) if accounts open. See their privacy policy.
• Cloudflare — manages DNS and forwards email to hello@reefcalcs.com. See their privacy policy.
• Amazon Associates — if you click an affiliate link to Amazon, Amazon may set cookies and collect data per their privacy policy.
• Google AdSense — will serve ads on this site once ad units are live, and operates the consent banner shown to EEA / UK / Swiss visitors. See Google's privacy policy and advertising technologies overview.
• Google Analytics 4 — counts unique visitors and measures page usage so we know which pages need work. IPs are anonymised before storage, and the CMP controls whether analytics cookies are set. See Google Analytics's data practices.

Embedded calculators

The calculator pages at /embed/<name> are designed for third-party sites to iframe. Those embeds load the same calculator JavaScript directly from reefcalcs.com. The host site cannot read your inputs or results because of standard browser iframe isolation. Embedded pages load no analytics and no ad scripts — only the calculator itself.

Changes to this policy

If we change how we collect or use data, the date at the top of this page will move. The substantive practices — calculations run in your browser, no account is required, and we set no first-party tracking cookies — are intentional and are not expected to change.

Contact

Questions about this policy: hello@reefcalcs.com.