Alkalinity, tested every 3 hours, by weight.
AlkScale is a planned automatic alkalinity tester for reef tanks. It weighs the water sample and the acid on a scale instead of counting pump steps, so there’s no pump to calibrate. Open reagent recipe. Designed to run locally with Home Assistant, or on its own with no controller and no cloud account.
$249 estimated (monitor) Nothing is charged today. No deposit, no card.
Concept stage, as of 6 Oct 2026. Nothing is built or tested yet. This page is a waitlist and a call for beta testers. What exists today
Run a reef with Home Assistant, or near Baltimore? Apply to beta test.
- AlkScale test, every 3 h
- Hand test, with the checker’s ±0.3 dKH ±5% spec
Show it as a table
What reef keepers say about the current options
Public forum posts, quoted as written. They are about today’s testers and kits, not about AlkScale. The last one asks for a DIY kit, which AlkScale isn’t; we quote it because it shows people want a cheaper way in.
I would use Hanna exclusively if the reagent was not 18.00 for 25/testReef2Reef, April 2026
Reef2Reef thread, 2024“maintenance on the machines became too much where I wasn’t enjoying the hobby”
“Reagents became too expensive”
“Kits! Sell me a kit, I’d buy it”
r/ReefTank, April 2026
How it weighs
An alkalinity test is a titration: add acid to a known amount of tank water until a colour indicator flips, then work out how much acid that took. AlkScale does the same thing, but it measures both amounts on a scale.
- 1The cup sits on a load cell.About 50 mL of tank water, weighed to a target of 0.01 g.
- 2Acid drips in from above.The scale reads how much actually landed. No pump steps are counted.
- 3A colour sensor watches through the wall.The indicator changes colour at the endpoint. The sensor tracks that change as a ratio of two colours, so it isn’t fooled by dye building up as the acid goes in.
- 4Nothing touches the cup while it weighs.Sample and drain tubes lift clear; the stirrer sits underneath.
Why weighing gets rid of pump calibration
Most automatic testers push acid with a small pump and count its steps. Each step is assumed to deliver the same volume. It doesn’t, quite: the tubing wears, warms and stretches, so the volume per step drifts, and you recalibrate.
By our estimate that drift is worth about 1–2% of the acid, roughly ±0.08 to ±0.16 dKH at 8 dKH. A scale doesn’t care how the acid got there. The target is to read about 6 g of acid to within 0.01 g, which would be closer to ±0.01 dKH on that one step.
The result is still worked out the ordinary way:
Worked example, illustrative numbers. Sample density assumes 1.024 g/mL; real units will measure or set it.
What weighing fixes
- Pump drift. The acid and the sample are both measured, not assumed.
- Tubing wear. Worn tubing changes how fast the acid arrives, not how much the scale reads.
- The calibration chore. No pump calibration step. You still check it against a hand test now and then.
How the measurement is designed to work
- Settled, then weighedThe load cell is given time to settle after the sample lands, and the scale watches the weight for a moment before any acid goes in. Any slow drift is subtracted from the result.
- The same stir-bar angle every timeEvery weighing is designed to be taken with the stir bar stopped at the same angle, so its magnet adds the same constant offset each time.
- Nothing hangs in the cupSample and drain tubes lift clear before every weighing, and readings are averaged.
Our goal is to match the precision of the $600 testers, not beat it.
Where this is today
Nothing is assembled yet, so here is exactly what exists and what doesn’t. This block changes when the status does.
- Stage
- Concept. No prototype has been built.
- Exists
- A written design: the drawing above and the planned parts list.
- An error estimate: the arithmetic in “How it weighs”.
- A test plan, with the pass marks set before any testing (below).
- This page: waitlist, price questions, beta applications.
- Not yet
- Any working hardware or firmware.
- Any measurement. Every number on this page is a target, an estimate or simulated.
- A final price, a parts quote, or the pre-mixed reagent bottle.
- Next
- Build a bench prototype, run the three tests, publish the raw numbers here, pass or fail.
Planned parts, monitor version
| Job | Planned part | Status |
|---|---|---|
| Controller | Espressif ESP32-S3 Wi-Fi module | Planned |
| Scale | 100–300 g beam load cellread by a 24-bit bridge ADC: TI ADS1232 or an HX711-class chip | Planned |
| Endpoint | ams OSRAM AS7343 spectral sensor, with LEDs14 channels; reads the colour change as a ratio | Planned |
| Pumps | 3 stepper peristaltic headssample, acid, waste and rinse; TMC2209 drivers | Planned |
| Stirrer | Small motor and magnets under the cup, stir bar inside | Planned |
| Tube lift | Lifts the tubes clear before each weighingmechanism not chosen | TBD |
| Leaks | Drip tray and leak-sense pad | Planned |
| Power | 12 V DC wall adapterno mains voltage inside, no battery | Planned |
From our design notes. None of these parts has been assembled or tested together, and any of them can change during prototyping. Links go to the part maker’s own page so you can check the datasheets yourself.
The test we’ll publish, either way
Before anyone is asked for money, the prototype runs these three tests. The raw numbers go on this page whether they pass or fail. Today all three are targets: the plots are empty because nothing has been measured.
-
Ten tests back to back on the same water. If the device is steady, the ten results sit close together.
Spread (SD) ≤ 0.05 dKH
-
Test a reference solution whose alkalinity is known, and see how far off the answer is.
Within ±0.15 dKH of the reference
-
Three real tanks, thirty days each, with the readings published next to the keepers’ own hand tests. This one is a reliability test: a hand checker is too coarse to judge accuracy, which is what the bias test is for.
At most 1 intervention a week, no missed tests, no leaks
Why a reference solution and not a lab report? Mail-in ICP labs measure elements, and alkalinity isn’t an element. And a common hand checker’s own spec is ±0.3 dKH ±5% of the reading, too coarse to prove a tighter result on its own.
The open reagent
The acid isn’t a secret. It’s dilute hydrochloric acid with a colour indicator already mixed in. Mix your own from the published recipe, or buy a bottle from us (planned). The device doesn’t check whose bottle it is; it checks how strong it is.
Mixing by weight on a kitchen scale is more repeatable than measuring by volume. Each new bottle, homemade or ours, is checked against a reference solution of known alkalinity before use: the same bias test as above. The indicator will be chosen during prototyping and published with the recipe. The 6,900 figure is our arithmetic (1 L of 1 N standard makes about 41 L of working acid, at about 6 g a test). It leaves out the indicator and the RO/DI water. Dilute, but still an acid: wear gloves and eye protection when mixing, and keep it away from kids.
For comparison, reagent prices on 6 Oct 2026
- Hanna HI772 refill: $18.99 for 25 tests, about $0.76 a test
- Neptune Trident ACM reagent kit: $49.99 for 2 months, $109.99 for 6
- Focustronic Alkatronic reagent: $110 for 4 L
Specs: targets and plans
Nothing below has been measured; there is no prototype yet. Design means how it is meant to work, Target a goal the tests will check, Planned a feature we intend to ship, Estimate our arithmetic, TBD not decided.
Measurement
- Method
- Acid titration, sample and acid weighed Design
- Endpoint detection
- Colour sensor through the cup wall Design
- Test interval
- Every 3 h, adjustable Target
- Sample
- About 50 mL Target
- Scale resolution
- 0.01 g Target
- Repeatability
- SD ≤ 0.05 dKH Target
- Bias vs reference
- ±0.15 dKH Target
- Test length
- About 10 min Estimate
- Measuring range
- Not set yet TBD
Reagent
- Acid
- 0.024 N HCl, open recipe Target
- Acid use
- About 1.4 L a month, a test every 3 h Estimate
- Waste
- About 450 mL a day, to the sump or a drain Estimate
Connectivity and software
- Radio
- Wi-Fi (ESP32) Planned
- Home Assistant
- MQTT with auto-discovery, local Planned
- reef-pi
- Local integration Planned
- Standalone
- Local web page, no controller needed Planned
- Cloud account
- None required Planned
Physical
- Power
- 12 V DC wall adapter Planned
- Size, mounting
- Not set yet; beside the sump, not on it TBD
- Dosing
- Not in this version; dosing head planned Planned
What it won’t do
- Test calcium, magnesium, nitrate or phosphate. Alkalinity only.
- Dose. This version only measures; a dosing head is planned, not part of this test.
- Talk to an Apex at launch.
- Replace a hand test entirely. Check it against one now and then, the way you would any tester.
Compared with what you use now
The others exist and work today. AlkScale doesn’t exist yet. Here’s the honest version, including the rows where it loses.
| Feature | AlkScaleconcept | Hanna HI772hand checker | Neptune Trident ACMautomatic, alk + Ca + Mg | Focustronic Alkatronicautomatic, doses | KH Guardianautomatic, doses |
|---|---|---|---|---|---|
| Price | $249 estimatedmonitor | $74.99 | $649.88without reagents | $593.99 | Not verifiedwe couldn’t confirm a price on the maker’s site, Oct 2026 |
| Can you buy it today? | No. Concept stage, no track record. Raw test data will be published either way | Yes | Yes | Yes | Yes, from the maker (we didn’t check US stock) |
| What it tests | Alkalinity only (planned) | Alkalinity, by hand | Alkalinity, calcium and magnesium | Alkalinity | Alkalinity |
| How it tests | Automatically, by weight (planned) | By hand | Automatically | Automatically | Automatically |
| Needs a controller? | No (planned) | No | Yes, an Apex | No | No |
| Doses too? | Not this version. Dosing head planned | No | No | Yes | Yes |
| Reagent, pack price | Open recipe: 1 L of 1 N standard makes about 6,900 tests, acid only (estimate). Our bottle: TBD | $18.99 for 25 tests | $49.99 for a 2-month kit | $110 for 4 L | Its own reagent |
| Local / Home Assistant | Local MQTT and Home Assistant auto-discovery (planned) | Not applicable | Through the Apex | Optional Apex link | Local web page |
Prices from Bulk Reef Supply, checked 6 October 2026: Hanna HI772 and refills, Trident and Alkatronic. KH Guardian: no price we could confirm from the maker’s site, so none is shown. Prices change; check before you buy. Product names belong to their makers; no affiliation.
Price, and the waitlist
The waitlist gets one email when the test results are published. The price questions tell us whether $249 is right before we build anything.
If it’s ever built, nothing is charged without asking you first.
Join the waitlist
One email when there’s news. No spam, no cookies, no ad trackers. To delete your signup, email us at alkscale@burakali.com and we’ll remove it within a week.
Next, if you like: a few taps about your tank and how you test, and four price questions. All optional, under two minutes.
You’re on the list. A few quick questions?
Thanks. You’re on the list.
What happens next:
- The prototype gets built and runs the three tests.
- You get one email with the raw numbers, pass or fail.
- If it holds up, we ask about the refundable deposit. Nothing happens automatically.
Beta testers: run one next to your usual test
We lend you a unit. You run it next to your usual alk test for 30 days and share the data. That data is how we find out whether AlkScale works.
- You doKeep hand-testing at least weekly, log the results, and tell us what broke.
- We doLend you the unit. Nothing is charged.
- The dataPublished with the results, without your name.
- PriorityTanks within driving distance of Baltimore (MD, DC, VA, DE, PA), so units can be set up and fixed in person. Home Assistant users anywhere.
- AfterThe $199 beta-program price (estimated) if it’s built.
Application received.
If your tank fits the first round, you’ll hear from Burak by email with the details (shipping or setup, what to log, how to return the unit) before any unit leaves the bench.
Not on the waitlist yet? Add your email there too for the test results.
Questions worth asking
Can I buy one?
No. AlkScale is at the concept stage: there is no prototype, and nothing is for sale. This page collects a waitlist, price opinions and beta-tester applications. Nothing is charged and no deposit is taken.
Aren’t there already testers without pump calibration?
Yes. Some testers avoid it a different way, for example with optical level sensors. Weighing is our way of getting there, and it measures the acid as well as the sample. We’re not claiming to be first.
Why a colour sensor and not a pH probe?
Anything dipped into the cup changes the weight as the water level rises during the test, and a pH probe also needs calibration, storage solution and replacing. A colour sensor looking through the cup wall touches nothing.
How does it know how strong my homemade acid is?
It won’t assume. The plan is that every new bottle, homemade or ours, is first run against a reference solution of known alkalinity, and the device works out the acid’s actual strength from that. It’s the same bias test the prototype has to pass.
Why 50 mL a test?
It’s a balance. A bigger sample uses more acid and sends more water back to the sump; a smaller one makes each 0.01 g on the scale count for more. At 50 mL and 8 dKH a test takes about 6 g of acid, so 0.01 g is under 0.2% of it.
Does it need a controller? What about Apex?
No controller needed: it’s planned to run on its own with a local web page. Home Assistant (MQTT auto-discovery) and reef-pi are planned. Apex is not supported at launch.
Is the acid dangerous?
At working strength it’s about 0.09% hydrochloric acid: dilute, but still an acid. Wear gloves and eye protection when mixing, and store it out of reach of kids and pets. The standard you mix from is stronger and needs more care.
Will it dose for me?
Not this version. A version with a dosing head is planned, but it isn’t part of this test and has no price yet. It would only come after the monitor has proven itself, with daily limits and an automatic stop.
What happens to my answers?
They’re stored (in Google Firebase) so we can decide whether to build AlkScale and at what price. This page sets no cookies and loads no ad trackers. We also record anonymous page views and button clicks (a random visit ID, the referring site and campaign tags) to see which links bring people here.
To delete your signup, email us at alkscale@burakali.com and we’ll remove it within a week.
Why I’m building it
I’m Burak Unlu, a computer engineering student at Johns Hopkins in Baltimore. AlkScale is my own project, not a university one. When I read how automatic alkalinity testers work, the weak spot I kept coming back to was the pump: a titrator that counts pump steps is only as good as its tubing. A scale doesn’t care about tubing.
There’s no data yet. Here is the order of things: build it, run the three tests, publish the raw numbers either way, then put units on real tanks with people who already test by hand. If that’s you, I’d like your help.
Burak UnluBaltimore, MD · alkscale@burakali.com