Hi, I saw your other thread too but I'll reply in this one for now... As for drilling, I can either help you out and drill a hole for you, or lend you my drill bits - but as Brad said I think the corner tanks have a better chance of having a tempered bottom. If you have polarized sunglasses, try looking at the glass with them on. Although I think you need there to be a fairly bright light available like direct sun when you do this. If you can see a checkerboard patterning, the glass is tempered.
Other alternatives are drilling out the back glass at the top for a "cup" style overflow. I'll use my FW tank as an example you can check out:
http://canreef.com/vbulletin/showthread.php?t=28505
The flip side is that, as Brad mentioned, there are external overflows. Here's an example:
http://www.jlaquatics.com/phpstore/s...ct_ID=of-cs100
They do have a few drawbacks compared to drilling, but not significantly so, as mentioned if taken care of properly, these do work quite well in a pinch. And before you go out and buy one I suggest to put up a "wanted" ad because dollars-to-donuts someone will have one lying around that they're not using that you could buy for less than buying new.
I have only 1 two year old (and another on the way), I can only imagine what twins would be like. I think I just felt myself age just thinking about it.
