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Reef Sand & Substrate Calculator
Reef Sand & Substrate Calculator — How Much Aragonite for Your Tank
Adding a sand bed to a reef aquarium is both aesthetic and functional — fine aragonite sand hosts beneficial denitrifying bacteria in its deeper layers and provides a natural, light-reflecting substrate that mimics the seabed. Getting the quantity right before ordering saves multiple trips to the store. Too little sand looks patchy and may not sustain a deep enough anaerobic zone; too much raises cost and makes the tank harder to clean. A typical shallow sand bed (SSB) for reef aquariums runs 1–2 inches deep — enough for aesthetics and surface bacteria but shallow enough to avoid anaerobic pockets. A deep sand bed (DSB) runs 4–6 inches and actively denitrifies the water column. This calculator determines the volume and mass of substrate needed based on your tank footprint, desired depth, and substrate type. CaribSea aragonite (e.g., Arag-Alive, Fiji Pink) has a specific density of approximately 13.9 lbs/gallon dry; standard quartz sand runs 11.7 lbs/gallon.
How to Use This Calculator
1
Measure your tank's length and width in inches (internal dimensions).
2
Choose your bed depth: 1–2" for a shallow sand bed (SSB) or 4–6" for a deep sand bed (DSB).
3
Select your substrate type — CaribSea aragonite is the most popular for reef tanks.
4
The result shows volume in gallons and weight in lbs, plus how many standard CaribSea bags to buy.
5
Add 10–15% extra to the calculated amount — rocks displace substrate, and you'll want fill-in reserves.
Healthy water = healthy corals
Shop our WYSIWYG coral collection — photographed individually so you know exactly what arrives.
Frequently Asked Questions
Should I use a shallow or deep sand bed?
Shallow sand beds (1–2") are easier to maintain — detritus stays on top where powerheads blow it to the skimmer. Deep sand beds (4–6") create an anaerobic zone that denitrifies (reduces nitrate to nitrogen gas), which is beneficial in heavily stocked systems but requires careful setup to avoid hydrogen sulfide pockets. Most modern reef keepers use SSBs or bare bottom.
What type of sand is best for a reef tank?
Fine-grained aragonite (0.5–1.5mm, like CaribSea Fiji Pink or Arag-Alive) is the most popular. Aragonite is the same mineral as coral skeleton (calcium carbonate) and slowly buffers pH. Avoid very coarse crushed coral for display beds — it traps detritus and is hard to clean. Silica sand (play sand) is not recommended as it doesn't buffer and can encourage diatom blooms.
How do I rinse new sand before adding it?
Many hobbyists skip rinsing bagged live sand since rinsing washes away beneficial bacteria. If using dry aragonite, rinse in a bucket with RODI water until water runs mostly clear, then add to tank gradually. Expect cloudiness for 12–48 hours — this is normal and will clear.
Does sand affect water parameters?
Aragonite sand slowly dissolves and can raise calcium and alkalinity slightly over time — this is generally beneficial. However, a very deep sand bed releasing old calcium can cause parameter confusion. Test parameters regularly when first establishing a sand bed.
