Hiya, If your tank is just a standard IBC type, I think you'll find it'll suck in (collapse) under vacuum and will hence not work.
There's an easy way to test - just fill it up, seal the lid, open the bottom outlet and watch! If the tank empties or holds the vacuum without losing its shape too much, then you're good to go! Just make sure you have as straight a run as possible from your tank to the trough, and put the inlet to the trough just below where you want the water level to end up. You'll probably need at least a 25mm pipe to ensure that the air bubbles can 'gulp' back properly and allow the trough to re-fill.
Of course for this to work, you'll also have to break the vacuum to re-fill the tank, which means you would have to fill it from a hose or similar, rather than say rain water run-off.
Let us know how it goes!