I just sanitized my 2.5G tank a few weeks ago.
Here is what I did, in a nutshell.
I think it's similar to what is on that post above, but it's short and sweet.
I used a solo cup - I dumped in 20 glasses full of scalding hot water, then 1 glass full of clorox.
Let it set for 30 minutes.
Dumped it out.
Rinsed it really well in the sink w/scalding water.
Squirted dechlorinator all over it.
Rinsed it again.
Turned on the shower as hot as it would go.
Set the tank in the shower and let the hot water run over it for about 35 minutes.
It worked like a charm!
As for your gravel vac, I would not use bleach on it because it is made of plastic and can absorb the bleach, then release it later whcih could be disastrous. If you're really concerned about it, you can soak it in hot REALLY REALLY salty water - that should help. Or just pick up a new one. they're not too terribly expensive.