Well, because it sounds a bit complicated.
It couldnt be simpler mate, all you are doing is setting up a 'fish-tank' outside with no fish in it. Kiddies can set up fish tanks

Look go down your local garden centre, buy a fairly small outdoor pond filter for £20.00 and 3 metres of 3/4" green pipe. Feed one end into the bottom of the IBC, but thread it through 2" pipe so it doesnt curl up and float, so you draw water into the pump from the bottom of the IBC and fix same diameter pipe onto exit port of pump and feed back into IBC. Start water flowing with syphon and fix to pump, hey-presto there you go. SIMPLES!