IMHO it's a shift in the demographic that visit 'forums' as a whole as Cranberry stated. I regularly visit a couple different genres of forums, auto, r/c, fish, and the slow down @ SWF is very similar to slower post counts at my other boards.
As long as we're being 100% honest, and I hate to be negative-nancy, but let me throw this out there, the shift is happening because of a 'different' mentally of newer members. There seems to be a lack of members that 'want to become experts.' It's better described on cars, people don't want to learn how their engine works, that just want to know how to fix their car's problem.
In SWF terms, I guess it's like people just want to know how to keep their Hippo tangs and clownfish well-enough. They don't want to say learn about how the actual collection process happens, the different families of fish, how fish classification happens, etc. Christ I think I'm one of the last ones that actually posts the scientific name of fish here anymore.
They also aren't interested in the same topics as the experts. Some really rare fish that might excite an expert, they view the same fish as pretentious because of how much it costs. Some people are just what to know if this light fixture is good enough to keep clams/SPS, they don't want to learn the in's and out of lumen readings, photo periods, etc.
The radio control hobby went through this a couple years ago. Before, all of the hobby grade cars, you basically had to know how to turn a wrench fairly well, otherwise the hobby was way over your head. Then came ready to run cars, out of the box ready to go. Anyone go buy a hobby grade r/c car. Then they turn to the boards and just want to know how to fix their car when it breaks. They don't want to learn about how or why it did.
And then these constant mundane (if I can use that w/o being to harsh) questions drive out the expert/old timers who get bored. Same thing with keeping saltwater fish now. Before, you either were an expert or became one because of the learning curve. Nowadays, people just want a reef tank. They don't want to learn everything there is about it.
