Work Out Your Substrate Needs
Enter your tank's footprint and how deep you want the substrate bed, and we'll work out the volume you need – plus bags of CaribSea live sand if you're going marine.
Bag count is based on CaribSea's own published coverage (~6.6 L per 20lb bag). We can't give you an exact bag count for every brand we stock – not every manufacturer publishes a coverage figure, and we'd rather say so than guess. Check the coverage stated on the bag for other substrates.
FAQ
How deep should my substrate be?
It depends on what you're keeping. 3–5cm is a common baseline for a display tank. Go deeper – 5–8cm or more – for heavily planted freshwater setups or livestock that likes to burrow. Bare-bottom is also a valid choice for frag tanks, quarantine tanks and breeding setups where easy cleaning matters more than a natural look.
Why can't you give me an exact bag count for every substrate you stock?
Some manufacturers publish a clear coverage figure – CaribSea states its Arag-Alive sand covers about 6.6 litres per 20lb bag, so we can calculate bag counts precisely. Others, like Seachem's Onyx Sand, don't publish an exact coverage depth per kilogram. Rather than invent a number for those, we'll tell you honestly when we can't calculate it – check the bag itself, or ask our team in-store.
Do I need substrate at all?
Not always. Frag tanks, quarantine tanks and breeding setups are often run bare-bottom for easier cleaning and disease management. It's a genuine trade-off between a natural look/biological filtration surface area and ease of maintenance – there's no single right answer for every tank.
Can I mix substrate types?
Yes – a common approach is a nutrient-buffering base layer (like Seachem Onyx Sand) under a finer-grained cap substrate for the visible top layer. This is common in planted freshwater aquascapes where you want the buffering benefit without it being what you actually see.
Shop Substrate
Onyx Sand's bag doesn't specify a coverage depth per kilogram – for a freshwater planted tank, choosing between the 3.5kg and 7kg bag comes down to your footprint. Ask our team if you're not sure how far a bag will go.