Simple definition: Substrate is the material lining the bottom of a pond, such as gravel, sand, or bare liner.
Detailed Explanation
Substrate affects how easy a pond is to clean, where beneficial bacteria can establish, and how waste settles. Bare liner is easier to clean but offers less surface area for bacteria than gravel does.
Why It Matters
The wrong substrate choice can make routine maintenance much harder, or trap waste in ways that are difficult to see and clean out.
Practical Example
Deep gravel beds look natural but can trap decaying debris underneath, which is why some pond keepers prefer bare-bottom liners for easier maintenance.
