Noob question:

[Funky_Fish14]

Waterflow is important in any aquarium for many reasons:

1. Helps keep poop/waste from settling on the bottom (Ie: under rocks where you cant see, etc...)
2. Helps distribute nutrients around the tank (not only do I mean growth nutrients to corals and stuff, but also pushes the ammonia/nitrite/nitrate around to the bacteria, which to them is nutrients, and helps keep your tank clean)
3. Provides oxygenation!

(4. discourages algae growth etc... etc...)

There are many other reasons but those first 3 are pretty big ones. Even if you have an XP4 on there, I know those dont put out a TON of flow, and its probably not picking up a lot of the gunk on the bottom.

Heck, even in a FW tank I personally would add something additional for waterflow, be it a big airstone, powerhead, or a HOB filter. All my FW tanks have at least 2 things providing waterflow/movement.

More flow = better!

Cheers,

Chris