For the life in your tank
Your tank.
Down to a science.
From your first fill to your weekly water change. Free aquarium calculators that remember your tank and make every number count.
A place to start.
Set up your tank once. Every tool knows it.
Your tank stays on your device. No account needed.
- 01
Set up your tank
Your dimensions, your water. Saved for next time.
- 02
Pick a tool
The right calculators, with your volume already filled in.
- 03
Test, enter, dose
Turn your readings into a plan, with the math shown.
The toolbox
Good care starts with a little clarity.
Set your tank once — every tool below reads it. Each one shows its formula and its source, and takes gallons or liters without asking.
The foundations
Setup & Volume
A little planning now.
A better home for everything that follows.
Tank Volume
Every good calculation starts with knowing how much water you have.
Find your tank volumeBuild your tank
One saved tank. The right starting point for every tool.
A little care, a lot of life
For your tankFreshwater & Planted
Clear water, healthy fish, room to grow.
Find your daily balance
For your tankSaltwater & Reef
Small adjustments. A more stable reef.
Keep the balance
Get salinity right
Behind a healthy aquarium
For your tankEquipment Sizing
The right equipment for the tank you actually keep.
Everything flows
from the right fit.
Filters, pumps, and cooling work together. Size each one for your water, your plumbing, and your room.
Your tank. Real conditions.Filtration
Circulation
Temperature & more
One tank, connected tools
Your tank connects it all.
Save your tank once. Your water type shapes the dashboard, and your volume follows you into every calculator.
- Freshwater Follow your cycle and plan your next water change.
- Planted Bring CO₂ and fertilizer dosing into your routine.
- Reef Turn your salinity, alk, calcium, and magnesium tests into a plan.
- Volume to the rim
- 78.5 gal · 297 L
- Water at the fill line
- 74.8 gal · 283 L
- Gravel bed
- 99.9 lb · 45.3 kg, displaces 4.5 gal · 17 L
- True water volume
- 70.3 gal · 266 L — 6% under the label, 10% under the rim
- Water weight
- 585 lb · 265 kg fresh · 601 lb · 273 kg salt
- Turnover target
- 280–420 GPH freshwater · 1,400–2,800 GPH reef
Calculated by the same engine as your tools. Dosing uses the true volume: dose "75 gallons" of conditioner into this tank and you're overdosing by 7%.
A little deeper
The why behind the numbers.
The nitrogen cycle explained
Ammonia → nitrite → nitrate, why it takes weeks, and how to know when it is done.
Read the guideFurther reading
- FreshwaterWhy "one inch per gallon" is wrongThe rule everyone quotes and nobody should use — and what to use instead.
- FreshwaterFreshwater parameters chartEvery target range on one printable page: pH, GH, KH, ammonia, nitrite, nitrate, temp.
- Problem solvingCloudy water: causes and fixesWhite, green or gray — each one is a different problem with a different fix.
- Saltwater & reefReef parameters chartAlk, Ca, Mg, salinity, nutrients — targets by coral type, on one printable page.
- Saltwater & reefRODI water: why tap water failsWhat is in tap water, what it does to a reef, and what a system really costs to run.
Math you can check
Every result comes from a published formula or a cited reference — named on the page, with a “show the math” breakdown using your own numbers.
Gallons and liters, equally
Liters, centimeters and dKH aren't a toggle we bolted on. Every tool takes either, remembers which you use, and formats results the way you'd say them.
Private by design
No accounts, no tracking dashboards. Your tank profile and test log live in your browser and nowhere else.
Honest recommendations
When a result suggests gear, it's the piece the numbers justify — and we say so when the cheap option wins. Some links earn a commission; that never changes the math.