If you (like me) bought a large unbaffled tank, then driving when its not full is annoying, not to mention a bit dangerous, I tried thinking of a way to divide the tank to stop me getting sea sick while driving along but fitting it through an 8" hole in the top would be hard. But I then found these things called baffle balls on a website, but at £40 for 10 of them I thought this was a bit expensive for a few bits of plastic. So I made some, very very simple, I just got about 20 plastic plant pots, used tie wraps (cable ties) to stick them together in pairs (base to base), then chucked em in, they float near the surface, water displacement is very minimal (if u get pots with thin walls like i did), and they work very well. Simple but affective. I tie wrap in pairs for 2 reasons, first so they r bigger and break the waves (so to speak) better, and secondly so they dont stack themselves while sloshing around (thus making them, less affective). Try it, totally works, and only costs a few quid!! FYI, swill pots with DI water before putting in tank, and decent sized pots, I used 2.5l black square ones, the plastic was quite flexible.