what i ahve done to "capture" my leos is I have my bright light on till about 6pm/8pm (around there) and i turn it off and immediately turn on my red lights. I set-up my camera next to the tank (well you can do this before you switch to red lights) and I white balance to papertowels, whatever is white (but you know, white under red light if that makes any sense). Some cameras have a remote control that comes with it, i just turn it on when my leos start moving around. To my knowledge nothing is out there as an acessory for the consumer market. what I think can be used are these new home kits radio shack has. they are like home security systems
here's an example, Lorex™ Remote Internet Video Security Monitoring System, $99
http://www.radioshack.com/product.asp?catalog_name=CTLG&category_name=CTLG_002_006_003_000&product_id=49-1025
acording to this it has a motion senser. you will probably need to go to radio shack and get an idea on wither you can hook up your sony to this and make it record when something moves. it uses av cables, so in theory it should work. But what might end up happening is the camera might not record and so you might need to use one of those crappy survalence cameras and if you camera has a camera passthrough hook the survalance camera to that.
i know probably your main concern is tapes, because dv tapes are moderately expensive. you can get one of these mini camera systems with the motion ssensor and hook it up to your vcr and just record. i think a vhs can hold 2-6 hours and costs about 1-3 bucks. that might be the easiest, cheapest alternative if the motion sensor doesn't work for the camera. what i am trying to figure out is your camera is going to have to be in either play or record mode to capture whatever is moving around. what i din't know is if it is is going to be like when you export from computer to mini dv (where your camera is typically in play mode and the computer switches it to record mode by itself) or if it's like when you hook you mini dv camera to a vhs, your going to have to be recording constantly inorder for it to work.
so if anything made sense at all, try to see if there's a remote for your camera, try to see if your sony can work with a motion sensor they sell at radio shack, or get a survalence system and just use your vcr. i've never done this before but i am interested to see if it'll work. It just seems to me ever since super8 is no longer in demand, it's harder to do the timelaps thing.