The statement that holds true for the amount of matter in a successful food web is: The total amount of matter remains relatively constant, but it is cycled through the ecosystem.

Here's why:

* Conservation of Matter: The fundamental principle of conservation of matter states that matter cannot be created or destroyed, only transformed. This applies to ecosystems as well.

* Flow of Energy: While energy flows through an ecosystem (from the sun to producers to consumers), matter is recycled.

* Decomposers: Decomposers play a crucial role in breaking down dead organisms and waste products, releasing nutrients back into the ecosystem. This keeps the matter in circulation.

Therefore, while the forms of matter change, the overall amount of matter within a closed ecosystem (like a food web) remains relatively constant.