Simply open your ~/.fluxbox/init and search for this line:
Make sure nothing of this is in the tools:
prevworkspace, nextworkspace, prevwindow, nextwindow
Reload your configuration from the menu and the toolbar arrows will be gone.
Toolbar can have these tools, in any order, separated by commas.
shows the name of the current workspace
displays minimized windows, all windows etc, it is the "taskbar"
the place for some applications to sit, like gaim or others
A clock based on the C strftime function
buttons for changing workspaces
buttons for changing the active window