The Silirub stuff is good. Both Silirub2 and Silirub AQ are safe to use. I recently used quite a bit of the Silirub 2 and found it cured really fast, and without that awful vinegar smell.
If you get it from an aquatics shop expect to pay through the nose. Even Dartfrog are cheaper, I got 310mls of Silirub 2 from there for £7.99 (I collected, so no shipping), where at a well known chain pet store it was £3.99 for 78mls of an aquarium brand that stinks awful and takes an age to cure. I also got 310mls of Silirub AQ off ebay for £7.69 including shipping, but haven't opened that yet so couldn't tell you if it's any good.
After doing quite a lot of reading on sealants. I managed to get some Dow Corning 794F neutral silicone today for £5.25 at a local DIY shop, I'll let you guys know how it is when I start my build.