You can try, but good luck. The frag stands a good chance of sliming and falling off the glue once it hardens. You could try onion bag netting or fishing line if your glue doesn't work.
I've seen rubberbands work well in the past. Another great idea, put some rock rubble in a very small plastic tupperware with somewhat high walls. Then put the kenya tree in the tupperware. The container blocks the sweeping flow and allows the frag to mount itself to the rubble. After ~5 days the frag usually has a footing on one of the rocks in the container. Then you can remove that and superglue the rock