could you give some info on what type of setup you have? That would be quite helpful. Because for example if you're using more than one pound of live rock per gallon of water, then i'd say you dont need the HOB
aquaclear at all, save for carbon occasionally.
However if you're doing a fish only tank and plan to use no live rock and just use the hob
filter, then yes, you need to run it during the cycle.
The cycle is not cycling the water. Very common misunderstanding imo
. Cycling means you're getting the bacteria that breaks down amonia to its final stage to grow on either the live rock (if you're using it) or the filter media (if you're using that instead of live rock).
So if you dont have the filter running during the cycle...well, do you see where the problem would be? There would be no water (which has the amonia in it to get the bacteria going) running over the media in the filter, which is what needs the bacteria in order to call it "cycled".
Hopefully that was clear and made sense lol. If not, just ask again