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The Aquarium Planner
An ecological calculator for the whole tank. Build it step by step and watch it fill; every choice is checked against a sourced dataset of 19 animals, 10 plants and 19 substrates.
Your tank is empty.Add animals in step 2, or drop in an example.
19 US galSet your tank size belowFrom the calculator
01Tank
Pick a standard size or enter your own, in inches. The drawing follows it.
From the calculator: . The planner works from its volume, footprint and height. Changing the size here replaces it.
Bowfront, cylinder, hexagon or bowl? Measure it in the calculator and it comes back here with the right volume.
02Animals
Tap to add. Tap again for one more. Each one swims to the part of the tank it lives in.
Add from a list instead
03Plants
Tap to add or remove. Each one goes where it grows: surface, attached, foreground or background.
Add from a list instead
How much of each plant to buy depends on the species and the look you want, so it isn't estimated here.
04Water
The green band on each slider is the range every animal you picked can live in.
05Bed
The substrate stack, bottom layer first. The drawing shows each layer at its real depth.
A new layer starts as pool filter sand; change it in its row.
06Light
Your fixture as it is. The planner gives the direction, not a PAR number.
Impossible Aquariums · The Aquarium Planner · impossibleaquariums.com/the-ecological-planner.html
07Your plan
Shared water
Findings
*** Sources disagree here, or no reliable figure exists.
CycleFrom your build above
Cycling this tank
Save itPlain text
Your build, in writing
Your tank and its results, ready to copy or hand to Aquarium AI for a deeper, personalised plan.
Aquarium planning, explained
How do I know if my fish are compatible?
Compatible fish share overlapping water needs (temperature, pH, hardness) and don't prey on or harass each other. The planner intersects the published tolerances of every species you add and shows the water range that suits all of them, plus any conflicts.
How many fish can I keep in my tank?
Stocking depends on adult size, territory, waste and filtration, not a simple inch-per-gallon rule. The planner flags any species that needs more space than your tank gives, using a sourced minimum tank size for each species.
What water parameters do my fish need?
Every species has a published range for temperature, pH and hardness. Kept together, you need water inside every range at once. The planner calculates that shared window from the animals you add, and tells you when no single water suits them all.
How long does it take to cycle a tank?
Published cycles run roughly two to eight weeks. The two nitrifying bacteria groups grow at different speeds, and plants and substrate shift the timing. The planner lists what in your build speeds it up or slows it down.
Do I need CO2 or high light?
Only if your plants and stocking demand it. More light raises demand; if nutrients and growth can't keep up, algae fill the gap, and the simplest fix is less light. The planner reacts to your wattage, height and hours and tells you the direction.
Just need volume and gallons?
The Aquarium Calculator gives gallons, litres, water weight and substrate for box, cylinder, hexagon, bowfront and bowl tanks, and sends the tank straight here. Open the calculator