any thoughts on this product
 

If I used one of my existing aquariums that are undrilled..... what do you think of this product... is it as safe as they claim?



http://www.lifereef.com/siphon.html

Any siphon based overflow is inherently not quite as fail safe as a drilled overflow but these products have been around a long time and generally work well. I used one (not the exact one you linked to, but similar) on my first tank in the 90's.

The faster the flow through them, the harder it is for an air bubble to get trapped and risk losing siphon. Plus if you can hook up say an Aqualifter pump to suck out air bubbles from the U-tube it should help keep it clear.