Twice a day is fine, just make sure all the food is eaten in a couple minutes. If say after 5 minutes there is still uneaten food, you're putting too much in.
What kind of plants do you have? Floating usually help more because they are close to the light, and tend to grow faster. Faster growth = more nutrients used (of which ammonia is a nutrient for plants).
Just test your water daily, and do frequent water changes to keep the ammonia (and later nitrite) levels low. Eventually both will be zero and you'll see nitrates rise higher than your base 5 ppm.
Cycling can take up to 8 weeks.