Water changes automated...

[BillT]

They were designed more for water changes, and removed when done.....but some had holes drilled to aid the siphon effect...

I have seem many fish rooms (50-200 tanks) set-up for either auto-water changes or as a big recirc. system with things like this as drains.
When I was running a research fish room, we had about 3,000 tanks running this way. When you have that many tanks and there is a way to for the siphons not to run, there will always be something not working right.
When dealing with big numbers of tanks, you may need a more dependable drainage system.

There are also hang-on-the-back boxes (with a siphon tube from the tank and a hole and tubing connector for the drain) made for doing this. With these you can see if the siphon is filled with air.

[Ron Sower]

Thanks guys. I've been thinking about doing something like this in the future for just a couple tanks for simplicity and less hassle. But I just didn't want to drill any glass.