you can get a large towel and also get a friend. and have the friend hold one end, you hold the other and then submerge the towel down the gravel. siphon out 50% of the water, and when the pacu swims over the large towel, lift it up.
you won't get wet too much since the water is half gone already, it'll probably just get on the inside of the glass.
and your pacu won't be able to smash the glass since he won't be able to build of too much speed