When your glow-in-the-dark garden pebbles doesn't glow enough, make sure that your follow the below instructions:
1) Do not stack pebbles on top of each other, make sure they are spread out to get even amount of sun.
2) Do not let the pebbles sit under the sun while it's still in the plastic package.
3) At night time, keep away from presence of light bulbs to see the glow clearly.
4) Follow the three easy steps above and you will enjoy the best outcome of these pebbles.