Siphoning with the fish in is the easy way...easier on the fish, too, in my opinion. It helps when the siphon tube and the intake end is matched to the gravel, so that you aren't constantly sucking up gravel and blocking the tube.
For instance, I use 5/16 tubing (easy to suck/start and it's moderately/safely fast for a 5gal). The siphon tube is stuck into the intake end
', a one-inch ID pill bottle. I taped a plastic rod to the side for grip/control. This gadget is strong enough to pickup debris without disturbing the gravel or plants too much. You may have to experiment with your size gravel.
If your fish is the curious kind, just be careful. But the suction doesn't seem dangerously strong.
When I'm in a hurry, I just pour the water in over my (clean) hand with a one-quart measuring cup (for control). This doesn't stir up the bottom or disturb the plants.
When I have time, my fish enjoy having water poured on them! Go figure...crazy Betta.