I'm in the process of plumbing the new tank and came up with the bright idea that it would be interesting to have the return flow mimic the bidirectional flow that is found in certain areas such as barrier reef channels. Since the tank has two return ports (one in each corner), I thought I could oscillate the return between the two corners on 6 hour cycles (with perhaps a bit of overlap) in order to mimic tidal cycles. The only ways I can think of doing this is to go with a pair of actuator valves (one for each return corner) driven by a timer. Another possibility would be a single 3 way actuator valve, but this reduces the movement to one or the other and does not allow overlap. The positive to this approach though is that one side will always be open, unlike the pair of valves approach where they will be closed unless they are powered open (unless I get valves that are open in the power off position). Therefore, if the power goes out on the tank circuit while the pump in the garage may still be going, the pump won't be pushing against a closed valve (unlikely to be sure, but still a possibility with potentially messy consequences). The challenge here is that either of these options are terribly expensive (several hundreds of $$) and I'm not sure the benefit is really there). Further down the list are devices such as Oceans Motions, but these are on a very short cycle and are really more wavemakers than current directors. If anyone has doone anything like this, or has suggestions on how to do this somewhat economically through the application of equipment from other hobbies / industries, your thoughts would be most appreciated! I had looked into using valves from pool and spa type places, but unfortunately these are not made for saltwater application. Thanks!