It was on 24h. I had a similar setup 10 years ago and I remember having to put the dripper on a timer too but i don't remember why. This time I did it because each time I put h2o2 on my plant it picked up, and the clawing is a sign of lack of o2 and overwatering. One more thing was the drain holes in the top bucket are tiny and few. I think they are pretty clogged up with roots. If I fill water from there it floods easy and drains slow. The timer makes sure it drains well, and roots get more air. The hydroton never actually dries, even the surface is visibly moist. I also have a massive bubbler in the res underneath the plant so its a hybrid, the roots are still in water down there. I wish I can remember why I switched to timer last time, I can't remember if it was to reduce splashing, or I ran into trouble.
It is 18/6 but I do have a light that is overkill. It fills the whole top of the tent and it is as bright as the sun. Raising it certainly helped, and I also dimmed it by 50w. I love this light. It wasnt even set to full blast. I tried cranking it up all the way and it drew over 700w! It was set at 450w from factory. This light is insane! Way better than my 100 dollar Amazon 100w one haha.