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Aquarium guides/Fish tank decorations

Fish tank decorations: fit, substrate and cleaning

Start with 1 to 2 inches of rinsed gravel or sand, deeper where rooted plants grow; burrowing fish such as kuhli loaches need soft sand, and planted-tank soil goes in as its bag says. Use decor sold for aquariums, or rock and wood that suit your water: limestone, for one, raises hardness and pH. Leave out pieces with sharp edges or gaps a fish could wedge itself into, and arrange everything so a siphon and a scraper can still reach the filter intake, the heater and every pane of glass.

Two aquascapers setting driftwood in a large tank
Shown: two aquascapers setting driftwood in a large tank. Photo: Abhik.Mazumdar.73, CC BY 4.0, via Wikimedia Commons

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Arrange it so you can still clean

Set the pieces in the empty tank before you fill it. Then check you can still get a siphon into the corners you want to clean, reach the heater and the filter intake, and lift the largest piece out past the lid and the center brace. Keep equipment at the water levels and clearances its manual gives.

Plan for your tank’s shape: on a 20-long plan the long, low footprint gives more floor for rock and wood than a taller tank of the same gallons.

Measuring substrate

To buy substrate, you need its volume: the length times the width times the average depth. The substrate calculator does it for you; for example, a bed of 30 × 12 inches sloping evenly from 1 inch at the front to 2 inches at the back is 30 × 12 × (1 + 2) ÷ 2 = 540 cubic inches, or 8.85 liters.

Buy by the volume or coverage printed on the bag; materials weigh very different amounts for the same volume, so a pounds-per-gallon rule of thumb can be well off. The substrate calculator does the sum for your tank and turns it into bags where the maker prints a density. The substrate’s weight goes on the stand: add it in the filled weight calculator.

Is it safe for your fish and plants?

Decor sold for aquariums is the safe choice. For rock and wood from elsewhere, check that it suits your water: limestone, marble and shells raise hardness and pH, which suits rift-lake cichlids and livebearers but not soft-water fish; driftwood tints the water brown and lowers the pH a little. Leave out anything painted, coated or of unknown origin, and anything with sharp edges or holes a fish could wedge itself into.

Build heavy rock straight on the bottom glass, not on top of the substrate, so it cannot slide or be undermined by digging fish.

Measure the water once the decor is in

Measure the water as you fill, with the decor in place: counting the buckets tells you how much the tank really holds, without guessing what the decor takes up. Use that amount in the water-change calculator.

If a big piece has to come out every time you clean the filter or reach the heater, move it now, before the water goes in. The cleaning routine

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