Ask Nerita
A Pro AI advisor that knows your tank. Ask about any species' parameters, temperament, diet, or breeding, or get help with your own water, cycling, and livestock. It answers with your actual readings in mind.
Freshwater, reef & brackish chemistry
Nerita watches your water chemistry, walks you through your cycle, and tells you the moment a parameter starts drifting, while there's still time to fix it.
Free to start. No test kit lock-in. Log the readings you already take.
Add Nerita to your phone's home screen, it runs like an app, online or off.
Nitrate climbing. Up 12 ppm this week. Time for a water change before your fish feel it.
Most tanks don't crash from neglect. They crash from a drift nobody noticed until the fish started to pay for it.
What Nerita does
Every tank is different. Nerita adjusts its targets and how loudly it warns you to the kind of system you actually run.
A Pro AI advisor that knows your tank. Ask about any species' parameters, temperament, diet, or breeding, or get help with your own water, cycling, and livestock. It answers with your actual readings in mind.
Reef (soft, LPS, SPS, mixed), FOWLR, fish-only, seahorse, coldwater, plus freshwater (community, soft, hard, coldwater) and brackish. Each one gets its own safe ranges and alert sensitivity, so an SPS tank gets a tighter trip wire while a community freshwater tank isn't nagged over numbers it doesn't need.
A day-by-day fishless cycle coach tuned to your water type. It reads your ammonia, nitrite, and nitrate and tells you exactly where you are. Free shows you the stage; Pro tells you what to dose and when it's finally safe to add life.
The dangerous moves are the fast ones. Nerita flags a rapid alkalinity, salinity, or temperature shift the moment it shows in your log, not after the damage.
Track your fish, shrimp, snails, and plants with photos and notes, so you know what's in the tank and what each new addition is asking of your water.
See each parameter's history at a glance and catch the slow creep, the gradual climb that's easy to miss reading by reading.
No proprietary strips, no subscriptions to test. Log the readings from whatever kit you already own and Nerita does the rest.
For reef tanks, log your alkalinity, calcium, and magnesium doses and Nerita works out your daily uptake, so you can set a schedule instead of guessing at it.
Run a quarantine tank with every parameter in full view, so you watch a new arrival as closely as your display tank until it's clear.
Keep a running journal of what you changed and when. So when a number drifts, the cause isn't a mystery two weeks later.
How it works
Tell Nerita what you keep and how big it runs. That sets your targets and how strict the alerts should be from day one.
Punch in your test results in seconds. Nerita scores each one against your tank's range as you go.
Steady guidance while you're cycling, and a clear alert the moment something drifts toward trouble.
See it in action
Living Room Reef
29 gal · Reef · Cycled
Temp
78.4 °F
Salinity
1.025
Alkalinity
8.4 dKH
Calcium
432
pH
8.1
Nitrate
6 ppm
Log readings
Tuesday · test day
Cycle Coach
Stage 2 of 4 · Nitrite appears
Your bacteria are converting ammonia into nitrite. Both may read at once. This is exactly what should happen.
Trends
Alkalinity · last 30 days
Every parameter scored against your tank's range, the moment you open the app.
What it tracks
Nerita follows the full chemistry panel for your water type, and knows what each number should read for your kind of tank.
Saltwater
Freshwater
Brackish
Pricing
Free records your water and shows you where every tank stands. Pro adds the coaching and the early warnings that keep you ahead of a crash.
Free
Record your water and see exactly where every tank stands today.
Pro
or $4.99 / month · includes a 7-day free trial
The coaching and alerts that catch trouble before it reaches your fish.
Where Nerita is going
Nerita is early, and we'd rather show you what's real than pretend it's all here. Here's what just shipped, and what's coming.
Import your history from a spreadsheet or another app and start with your whole record instead of a blank slate. Available today.
Install Nerita on your iPhone or Android home screen and it runs fullscreen like an app, with offline logging. Available today.
Point your camera at your test kit or Hanna checker and let Nerita read the value and log it for you.
Saltwater ponds are an emerging kind of build, and they run on the same marine chemistry Nerita already tracks. They're first in line, with planted aquascapes and other setups to follow.
Pull readings automatically from popular monitors like the Neptune Apex and Seneye, so your probe data flows into Nerita without hand-logging.
Start logging in minutes. Let Nerita keep the watch so the next swing doesn't catch you off guard.