Hi Jan
I have had a couple of days to calm down, current mode "relaxed".
I am glad to read that you are doing the water changes. The danger is, as the tank is currently cycling you could get lethal doses of ammionia and then later nitrite.
The number of water changes is dependant of how quickly your ammonia builds up to dangerous levels. I am guessing with your stocking it is pretty rapid, but maybe someone else could be more precise.
Once your tank has cycled (maybe a week, if you have added the old filter media) you can relax the water change regime a bit. Until then, unless you are closely monitoring your ammonia and nitrite levels, I would go with 2 x 25% water changes per day. I am a novice, so others may be able advise you better.
I personally don't believe adding by cycle helps, but don't know of any harm caused by adding it.