I have never seen a tank with a tide effect, basically water flowing on one direction for 6 hours, then the other, done twice a day. My only thought would be that in such a closed environment, the hydro dynamics would have the water coming back of the far wall in a counter-current...which would basically ruin the effect you were looking for. Then again, in practice, it still might work well, and I am sure would produce a random current.
I have seen several tanks with timed "dumps" of water at high speed coming from higher up. generally they are referred to as "surges" and basically involve pumping water from your sump up to another tank located above (a few feet above) your display tank. At given intervals (like every 4 minutes) the surge tank releases all the water at once through high output tubes, into the display tank, and then the process starts all over again.
I know this is not what you are talking about, but basically both of them are just a different way of simulating varied currents in your tank. The tanks I have seen this surge system on are amongst the prettiest I have ever seen. They can have low levels of water movement from powerheads and closed loop systems, because every few minutes, the entire tank gets whacked with a bunch of water in fairly random currents....it is really cool to watch as well.
I am not good at the plumbing portion of this hobby, but I have heard it is quite difficult to get this system working correctly (mostly to do with (i) trying to keep an acceptable water level in your sump so it doesn;t affect your skimmer, and also (ii) having your display tank being able to handle a ton of water being dumped in at once which may involve creating additional overflowes or enlarging your existing overflows), but once it is working, then there are no concerns.
Maybe a surge system is a viable option for you?
HTH
Stewart
