Substrate types compared: gravel vs. sand vs. planted soil

Substrate is the stuff on the bottom of the tank. It anchors plants, hosts beneficial bacteria, and — for bottom-dwelling fish — is a welfare issue, not a decoration choice. Here's the honest comparison.

	Gravel	Sand	Planted soil (aquasoil)
Best for	General community tanks; beginners	Bottom dwellers (corydoras, loaches); natural look	Planted tanks
Depth	1–2"	1–2"	2–3"
Cleaning	Gravel vacuum works well; debris falls between grains	Debris sits on top — hover the siphon, don't plunge	Don't deep-vacuum; it breaks down over 1–2 years
Fish welfare	Use smooth, small grain for bottom dwellers — sharp gravel injures barbels	Ideal for diggers and sifters	Fine for most; softens/acidifies water (good for many plants and soft-water fish)
Plants	Inert — needs root tabs for heavy root feeders	Inert and compact — root tabs help; fine for easy plants	Nutrient-rich — best plant growth, no tabs needed at first
Watch-outs	Rinse thoroughly before adding (dust!)	Rinse extremely well; very fine sand can compact — stir gently or keep Malaysian trumpet snails	Releases ammonia at first — perfect for fishless cycling, terrible with fish already in

How deep?

1–2 inches — plenty for fish-only tanks. Easier to clean, less trapped debris.
2–3 inches — gives plant roots room and lets you slope it (deeper at the back looks great).
More than 3 inches of fine sand can develop anaerobic pockets — if you go deep, use gravel or soil, or keep it stirred.

How much to buy?

Use the substrate calculator: enter your tank's footprint and desired depth. As a sanity check, a 2-inch bed in a standard 20-gallon tank (24"×12") needs about 32 lb of gravel. Always round up to the nearest bag — running short mid-setup is miserable.

Rinse everything. Every substrate ships dusty. Rinse in a bucket until the water runs mostly clear, or your new tank will look like milk for days. (It clears, but why start that way.)

Next: cycle the tank before fish arrive · stocking, done conservatively