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A “10-gallon” tank rarely holds 10 gallons of water. Substrate, hardscape and the gap under the rim take up space, and that matters when you dose fertilizer, remineralizer or medication. This calculator gives you the tank’s total volume, a realistic estimate of the water it actually holds, and how much substrate you need for the depth you want.
How to measure your tank
- Measure inside the glass if you can. Outside measurements include the glass thickness and overstate volume by a few percent.
- Height is from the bottom glass to the top of the frame, not to your water line — the calculator already subtracts a 1 in (2.5 cm) gap.
- Bow-front tanks: measure the depth at the sides and again at the deepest point in the middle.
- Sloped substrate: enter the average depth — for example, 1 in at the front and 3 in at the back averages 2 in.
How the numbers are calculated
Volume is the footprint area multiplied by the height. One US gallon is 231 cubic inches and one liter is 1,000 cubic centimeters. For bow fronts we add the curved section as a parabolic segment (two-thirds of the bow’s extra depth × length). The water estimate subtracts the substrate volume and the top gap, then another 5% for rocks, wood and plants.
How much substrate do shrimp tanks need?
| Substrate | Typical depth | Why |
|---|---|---|
| Active soil (for Caridina) | 1.5–2.5 in (4–6 cm) | Enough buffering capacity to hold pH low for 12–18 months |
| Inert sand or gravel (Neocaridina) | 1–2 in (2.5–5 cm) | Plants root well; deeper beds can trap waste |
| Planted with root feeders | 2–3 in (5–7.5 cm) | Room for root tabs and heavy root systems |
Common tank sizes
| Tank | Inside dimensions (approx.) | Total volume |
|---|---|---|
| 5 gal | 16 × 8 × 10 in | 5.5 gal / 21 L |
| 10 gal | 20 × 10 × 12 in | 10.4 gal / 39 L |
| 20 gal long | 30 × 12 × 12 in | 18.7 gal / 71 L |
| 60-P (60 cm) | 60 × 30 × 36 cm | 64.8 L / 17.1 gal |
| 29 gal | 30 × 12 × 18 in | 28 gal / 106 L |
FAQ
Why is my tank’s real volume less than its label?
Manufacturers label tanks by nominal size, often measured to the very top rim. Once you add 2 in of soil, a hardscape and leave a gap at the top, a 10-gallon typically holds 7–8 gallons of water.
Should I dose using total or net volume?
Use the net (water) volume for medications and remineralizer, especially in shrimp tanks where overdosing copper-sensitive or mineral-sensitive animals is a real risk.
How heavy will my tank be?
Water weighs about 8.34 lb per US gallon (1 kg per liter). Add roughly 10–15% for glass, and substrate at around 1–1.5 kg per liter, when checking your stand or shelf.
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