Marine Aragonite Sand Complete Guide: DSB vs Bare Bottom
Sand bed choice quietly shapes every reef tank‘s long-term biology, yet it gets decided in ten minutes at the shop when it deserves as much thought as rock or lighting. This marine aragonite sand complete guide from Gensou Aquascaping at 5 Everton Park walks through grain size, depth strategies, DSB (deep sand bed) versus shallow versus bare bottom, and the Caribsea product lines stocked at Polyart with current SGD pricing. Pick a substrate and depth aligned with your stocking and flow plan — retro-fitting the sand bed of a stocked reef is the most miserable maintenance task in saltwater.
Why Aragonite Over Silica
Aragonite is calcium carbonate — the same mineral that forms coral skeletons. It buffers alkalinity and calcium as it slowly dissolves, stabilising pH at reef-friendly 8.0-8.3. Silica-based play sand from hardware stores is inert and can leach silicate that feeds diatom blooms. Use marine-grade aragonite only: Caribsea Aragamax Special Grade, Fiji Pink, Arag-Alive Bahamas Oolite, or the generic white aragonite sold in 9 kg buckets at Reef Depot SGD 35-55.
Grain Size Matters
Fine sand (0.25-1.5 mm, “oolite” grade) packs dense, looks natural, and allows sand-sifting gobies to dig. Downsides: storms in strong flow, clogs under rock, and can compact to anaerobic pockets. Medium sand (1-2 mm, “Special Grade”) is the middle ground — stays put in moderate flow, supports Nassarius snails, and suits most mixed reefs. Coarse crushed coral (2-5 mm) retains detritus and grows algae fast; skip it unless you specifically want a crushed coral look for a FOWLR tank.
Shallow Bed (2-4 cm)
Most modern Singapore reef tanks use a 2-4 cm shallow aragonite bed — enough to look natural and host a small sand-sifting fauna, shallow enough that detritus can be vacuumed during water changes. For a 75 L nano, 7-9 kg of Caribsea Special Grade covers the footprint to 3 cm. For a 200 L build, 18-22 kg. Shallow beds are low-maintenance and forgiving; they suit mixed reefs, LPS dominant tanks and almost any first-time build.
Deep Sand Bed (10-15 cm)
A DSB of 10-15 cm creates a genuine anaerobic zone in the bottom layer where denitrifying bacteria convert nitrate to nitrogen gas. It also hosts a rich infauna of pods, worms and tiny stars that feed the reef. DSB proponents cite lower nitrate and higher biodiversity. Drawbacks are real: the bed locks away detritus over years and eventually releases phosphate and hydrogen sulphide during disturbance events (“old tank syndrome”). DSB belongs in a 450 L or larger tank with commitment to 10+ year lifespan — not a 75 L nano.
Bare Bottom Approach
SPS-focused reefers increasingly run bare-bottom tanks — no sand, glass directly visible. The argument: detritus is easily siphoned, flow is not impeded, and nitrate/phosphate are easier to keep low for SPS colouration. The cost is aesthetic (glass bottoms look industrial) and biological (no infauna, no buffering). Bare bottom suits experienced reefers chasing ultra-low nutrient SPS tanks. Skip it for your first build.
Caribsea Product Lines at Polyart
Polyart in the Serangoon cluster carries the main Caribsea lines. Aragamax Special Grade (1-1.7 mm, 9 kg bag SGD 35-45) is the standard pick. Fiji Pink (0.5-1.5 mm, 9 kg SGD 40-55) has a slightly pink tint that looks natural with coralline. Arag-Alive Bahamas Oolite (0.25-0.75 mm, 9 kg SGD 50-65) is live wet sand seeded with bacteria but the shelf life matters — check dating. Reef Depot also stocks generic white aragonite at SGD 28-35 per bag for budget builds.
Rinsing and Initial Fill
Rinse dry aragonite lightly in RO water — a few passes to remove dust, never full rinse which strips beneficial calcium surface chemistry. Add sand before rock so the aquascape sits on a flat base. Pour salt mix slowly over a plate or dish to avoid disturbing the sand surface. Expect 24-48 hours of cloudiness as fine particles settle — running a filter sock or floss captures the bulk. Resist the urge to run powerheads at full speed during fill; storms carry sand onto rock where it cements to unflattering dust patches.
Sand Bed Maintenance
Vacuum the exposed sand surface with a Python siphon during weekly water changes, focusing on detritus zones under overhangs. Do not disturb deeper layers — the goal is surface cleanliness, not full turnover. Nassarius snails (SGD 3-5 each at Reef Depot) and sand-sifting gobies like Valenciennea strigata (SGD 35-55 at Iwarna) till the top 1-2 cm naturally. In a shallow bed, replace the top 2 cm every 4-5 years if it develops persistent detritus build-up despite flow and cleanup crew.
Flow and Sand Storms
Match sand grain size to your powerhead flow. A 75 L nano with a single Jebao SLW-10 at low speed tolerates oolite-grade fine sand. The same tank with two MP10s on Reefcrest mode storms fine sand onto rockwork within a week — use medium-grade Special Grade instead. Place powerheads pointing parallel to the substrate, not down at it. A sand storm in front of corals is a flow design error, not a sand problem.
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