HOW IT WORKS
Every reading, checked the way an experienced reefer would.
How a tank gets its grade, what that catches that a range check cannot, and what the app looks like once your Apex is connected.
HOW GRADING WORKS
One number, looked at five ways.
Level is only the first question. Pick a check to see what it asks of thirty days of the sample tank's alkalinity, and what it says today.
AlkalinityTRIDENT · 30 DAYS · SAMPLE TANKTARGET 7.8–9.5 dKH
FLAG
7.0 dKH, below the 7.8–9.5 targetThe target comes from what the tank houses: a mixed reef with a few SPS, sensitivity 4. A one-size range of 7 to 11 would call this fine.
WHAT MAKES IT DIFFERENT
Every reef app has a chart and a chatbot. Here is what is behind ours.
Compare every row with
THE CHATIt reads your tank before it writes a word, and then it does the work.
AGENTS
Specialist agents read your tank before anyone answers.Your question goes to specialist agents for your readings, your history, your equipment and a curated reef knowledge base. They report back, and only then is the answer written, with your own numbers in it.
REEFGPT
READINGSHISTORYEQUIPMENTKNOWLEDGE
↳ONE ANSWERABOUT YOUR TANK
SPECIES
It checks a fish against your tank, not the internet.Minimum tank size, adult size and temperament come from a reference of 377 species, and are checked against your gallons and the livestock you already have.
REEFGPT
“Can I add a purple tang?”Not in your 40. Purple tangs need about 125 gallons and a six-foot tank to swim.
ACTIONS
It does the paperwork. You tap confirm.Mention new livestock or ask for a reminder and it prepares the change for you to approve. If “a blenny” could be several fish, it asks which one first.
REEFGPT
ADDSalarias fasciatusConfirm
ADD REMINDER20% water change · Sep 26Confirm
THE NUMBERSEvery reading is checked the way an experienced reefer would check it.
GRADE
Targets that fit what your tank houses.Tell it what lives in the tank, from softies to SPS-dominant, and every target tightens to match. Each parameter is then checked five ways by fixed rules, so the same readings always get the same grade.
REEFGPT
ALK 7.0 dKH · MIXED REEF, A FEW SPS
TARGET 7.8 TO 9.5LEVELSWING ✓DRIFT ✓
WARNING · BELOW TARGET FOR THIS TANKNOISE
It knows how noisy each instrument is.A Trident test and a pH probe wobble by different amounts. A move smaller than the instrument's own noise is not news, so you are not trained to ignore the app.
REEFGPT
INSIDE TRIDENT NOISE
0 FLAGS
0 FLAGS
SILENCE
A flat line is a question, not good news.When a Trident or probe stops reporting, its last value can sit there looking perfectly stable. ReefGPT checks how old every reading is and asks for a retest instead.
REEFGPT
PhosphateTRIDENT NP0.06ppmNOTHING FROM THE NP IN 8 DAYS · RETEST
PROBES
It will not guess which probe is your tank.An Apex can report three pH probes, one sitting in a calcium reactor. Exactly one probe is graded for each parameter, and when two could be your display, it asks you instead of picking.
REEFGPT
Two probes read pH. Which one is your tank?
PH · 8.18 · DISPLAYREACPH · 6.61 · REACTOR
DOSING
Dosing is counted dose by dose.Every dose your Apex logs arrives with its own timestamp, so each day is an exact total, even on days you never opened the app. A head that stops is noticed, because it is compared with its own normal.
REEFGPT
DOSMG · MAGNESIUM · SEP 16 TO 22
22 mL
22 mL
22 mL
9 mL
0 mL
0 mL
0 mL
GAPS
It never invents a reading.A missing test stays missing. It is never bridged with a smooth line or filled with a zero, and a chart only draws what your tank actually reported.
REEFGPT
NO DATA
SHOWN AS NO DATA
SHOWN AS NO DATA
YOUR TANK, YOUR KEYSBuilt so a mistake cannot reach your livestock.
ACCESS
It never has your password, or the keys to your tank.You share view-only access inside Apex Fusion. It cannot switch an outlet or change a dose, and your tank is matched by serial number, so two tanks both called “Display” can never be mixed up.
REEFGPT
SHARED WITHapex@reefgpt.netACCESSVIEW ONLYMATCHED BYSERIAL AB12:3456
None of this is a feature you switch on. It is how every number is handled.Request trial access
INSIDE THE APP
What you actually see, screen by screen.
These are the app's own screens, drawn with a sample 40 gallon tank. Nothing here is a concept.
Tank Condition
WARNING
Stability Score
76/100
97% confidence
1 issue · 1 retest
•Alkalinity is 7.0 dKH, below the 7.8-9.5 dKH target
Phosphate hasn't come through from Neptune Trident NP in 8 days. Sync, or check the probe is still reporting.
Sensitivity:4 · Mixed reef, a few SPS
Alkalinity
6.96
Calcium
432
Magnesium
1346
Nitrate
11.9
Phosphate
0.06
tested 8d ago
pH
8.24
Temperature
78
Salinity
1.0262
ORP
382
Telemetry
Alkalinity ▾1D3D1W
Notifications
Magnesium has stopped dosing
It normally does about 22 mL a day and the last 24 hours were 0 mL. Check the container level and the line.
DosCa
Calcium
38mL/day
Measured by your Apex, spread through the day
Calcium
DosMg
Magnesium
0mL/day
Measured by your Apex, spread through the day
Magnesium
September 2026Reef care calendar
MonTueWedThuFriSatSun
31
1
220% water change
3Feed frozen mysis
4
5
6
7
8
9
10Feed frozen mysis
11
12
13
14
15
16
17Feed frozen mysis
18
19
20
21Trident reagents
22
23Test PO4Clean skimmer
24Feed frozen mysis
25
2620% water change
27
28
29
30
1
2
3
4
Fishx2Ocellaris Clownfish
Amphiprion ocellaris
FishRoyal Gramma
Gramma loreto
FishYellow Watchman Goby
Cryptocentrus cinctus
CoralHammer Coral
Euphyllia ancora
Coralx2Acropora
Acropora sp.
InvertebrateSkunk Cleaner Shrimp
Lysmata amboinensis
Weekly AI Summary
Sep 20, 12:00 AM
Nitrate rose from 9.3 to 11.2 ppm this week with feeding at twice a day, and alkalinity kept sliding, from 7.5 to 7.1 dKH. No phosphate test came through after Sep 14.
WHY NOT A SPREADSHEET
Logging is not the hard part. Reading it is.
Most reef apps are a nicer place to type numbers. The difference shows up after the numbers are in.
SpreadsheetTypical reef appReefGPT
Readings arrive without typingNoSome connect a controllerApex, Trident and Trident NP
Knows a normal wobble from a real moveNoFixed alarm rangesGraded against each instrument’s noise
Notices a probe that went quietNoShows the last valueAsks for a retest when a reading gets old
Notices a doser that stoppedNoShows the dose you typed inCompares every head with its own normal
Answers questions about your tankNoA general chatbot, if anyReads your readings, doses, livestock and notes
Works with a test kitYesYesYes, graded the same way
CLOSED TRIAL
Put ReefGPT on your tank.
We are letting reefers in a few at a time, Apex owners first. It is free while the trial runs, and there will always be a free tier.