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45 cm Tank (18 in) — Water Volume, Water Change, Heater, Filter & CO2 Calculator

Setting up a 45 cm Tank (18 in)? Instead of googling real water volume, water-change amount, heater wattage, filter flow and CO2 bubble rate every time, enter your numbers below and get all the figures for this tank size at once. Real volume is auto-adjusted to about 80% of the brim-full volume to account for substrate and hardscape.

Quick Calculator

Brim-full volume
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Real volume (est.)
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Water change per session
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Dechlorinator amount
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Recommended heater
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Recommended filter flow (5–10× turnover/h)
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CO2 bubble rate guide (bps)
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Small-fish stocking guide
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These are general guidelines. Optimal values vary by livestock, plants and product. Dechlorinator defaults to 10 ml per 10 L — override with your product's label.

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Popular fish & plants for this tank size

Difficulty: 初心者〜中級

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Gear to set up this tank size

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Canister filter (e.g. Eheim Classic)
Stable filtration is most of a successful setup. Aim for 5–10× turnover/h.
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Heater + thermostat
Pick wattage at or above the calculator's figure. Guard cover recommended.
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Water conditioner (Tetra / Seachem Prime)
Dose by water-change volume × label rate. See the calculator's dechlorinator output.
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Water test kit (API Freshwater Master)
Measuring pH/nitrite/nitrate slashes failures. Essential during cycling.
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Aquarium LED light
For plants, check PAR/spectrum, not just brightness.
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Aqua soil / substrate
Main reason real volume drops to ~80%. Re-check water change in the calculator.
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Fish food (flakes / wafers)
Leftovers foul water. Feed small amounts, a few times.
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Pricing

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Keep conditions stable with a water log

A logging feature for water-change dates, temperature, pH and dosing — to catch problems early — is in the works.

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FAQ

How much water does a 45 cm Tank (18 in) actually hold?

About 41 L when brim-full; the real volume after substrate and layout is roughly 32 L.

How much and how often should I do water changes?

A common guide is 20–30% of real volume once a week. Increase frequency for heavily stocked or heavily fed tanks.

What heater wattage do I need?

For this tank size, roughly 81–113 W is a good guide. Pick the higher end for cold rooms.

Calculate for other tank sizes