My guppies, adults and fry, striking bottom?

Question

My guppies, both adult and fry of all ages are repeatedly striking off the bottom of the tank and the ornaments. There is no signs of white spots at all, and I can rule out ich entirely having seen it before. What else could it be? Is there any reliable non-chemical ways of treating it? If not what chemicals do I need? Do I need to remove carbon filter for this?

NB My neon tetra's do not seem to be affected, and these are the only 2 species in the tank

Answer 1

try doing a partial water change

Answer 2

This sounds like "flashing",and indicates some sort of skin irritation. Could be parasites,or ammonia burns, or any number of other things.