Lay out the cleaning route first
Before filling, arrange the proposed pieces so you can reach the intake, thermometer, heater and glass. Check that a siphon can enter the areas you intend to clean and that a lid or brace does not prevent removal of a large piece. Keep the exact equipment manual’s clearances and water-level requirements.
On a 20-long plan, a long footprint and low height create a different layout from a taller tank. Measure your real tank rather than copying a display photograph.
Separate three measurements
Bulk substrate volumeLength × width × average bed depth. Includes spaces between grains.
Displaced waterWater excluded by submerged contents. A measurement or explicit estimate.
Dry weightThe mass added to the tank before water. Count each item once.
Use the substrate worksheet for bulk volume. For example, a bed measured at 30 × 12 inches, sloping evenly from 1 to 2 inches, has 30 × 12 × (1 + 2) ÷ 2 = 540 cubic inches, or 8.85 liters. Those are example measurements, not a recommended bed depth.
Use the bag’s own volume or documented coverage to buy material. Do not turn that result into pounds with a generic density.
Choose material for the actual care plan
Ask what the product is intended for, how the maker says to prepare it, and whether it suits the water, plants and animals in the care plan. Appearance does not settle suitability. Unknown coatings, previous treatments or an uncertain material need an answer before the item enters the tank.
Heavy or unstable arrangements also need an appropriate support method. The filled-weight worksheet adds loads; it does not approve a rock structure, tank base or floor.
Finish the water and maintenance plan
A measured fill with the contents in place can establish working water without guessing a displacement percentage. Include connected water once. Carry that amount into the water-change calculator.
Write down which pieces must be lifted to clean or service the filter. If that requires moving heavy decor every time, revisit the layout before filling. Use the cleaning sequence for the equipment and water-handling steps.