You can use them, yes, but Silicone II actually has on the label "not for aquarium use." The problem with Silicone II apparently is that it will not hold up to long-term continuous submerged use so it is not a good choice as a structural bonding agent.
In a pinch Silicone I can be used but I would just like to actually have onhand the stuff that GE goes out of their way to recommend for aquarium use.
I have actually used Silicone I in the past on baffles in the sump and the silicone actually discoloured after a few weeks of use. It appears to be holding acceptably still after 1 year but the silicone is noticeably yellow. It just looks fugly... So that's why I'm going out of my way this time to get some RVT100.
While we're on the topic of silicones... Incidentally in my search I called Bow Valley and asked what they use, I was told "GE Construction 1200". And they sell tubes of that for $8 each.. (Embarrassingly, apparently I knew about GE1200 already:
http://www.canreef.com/phpBB2/viewtopic.php?t=13244& ... sigh
)
There you go, I bet that's more about silicone than anyone really wanted to know!!!
