If you’ve never heard of the Switching Current Water Director, aka the SCWD (pronounced ‘squid’), congratulations because you’ve been a reef hobbyist in in a very different era or reef keeping. Before we had all the digital bells and wireless whistle on every type of reef aquarium equipment, manufacturers had to get a little more steampunk with the clever mechanisms they employed to enhance what our equipment could actually do.
The SCWD is the total embodiment of this period of time with a clever water-powered mechanism that automatically alternated water flow from one side of the tank to the other. The speed of the switching was directly proportional to the water flow rate so the faster the flow, the faster the SCWD would switch which outlet it directed water out of.
In a clean-room reef tank the SCWD is an awesome device that fully lives up to its design and expectations, but our reef tanks are the diametrical opposite of a clean room with dozens of different groups of animals are competing to grow on every surface that is exposed to ‘live’ reef aquarium water. This means that for most users of the SCWD on reef tanks of the late 90s and early 2000s the device worked perfectly for about one or two months before it invariably failed to alternate the water flow as it once did.
The 3/4″ version of the SCWD is completely sealed so servicing the machine was next to impossible but a follow up 1″ version had a removable cap so users could (theoretically) clean and or replace internal components. Despite these improvements users often had more issues with the one inch version of the SCWD, often just gutting the internals to turn it into a glorified plumbing T but about one in ten SCWD of the 3/4″ model would last up to a couple years before succumbing to mechanical wear and tear.
With so much more controllability to our reef aquarium water pumps there’s much less of a need to look towards gadgets like the SCWD to provide alternating water flow in our reef tanks but it’s fun to take a trip down memory lane and realize how far the hobby has progressed in the 20 years since the SCWD first hit the reefing hobby. To fully appreciate the origins of the SCWD take a look at the short promotional video which has clear styling and soundtrack of the 1990s but was uploaded to YouTube by the parent company 3iQ Ventures as recently as 2017.
The SCWD might be a pretty old reef aquarium product but since there’s no app or electronics there’s no reason you can’t use one today, provided that it is used in just the right application, probably a freshwater aquarium where biofouling organisms are a fraction of what we deal with in reef tanks. We picked up a couple units at one of our oldest local fish stores, Neptune’s Tropical Fish, one to put on the antique reefing shelf, and another that we just might consider for installing in a future setup, knowing full well that it’s working life will be quite limited.
