I use these. Spoonful a day per piggie is all you need. These are one with the lowest calcium content, but still can't be overfed. I have 9yrs old and he's been fed these for past 3or4 years. They never leave a single bit.
Just seen your location, so guessing you can't buy them from zooplus. Avoid the 8kg bag as it's not same as the smaller bags. We buy the 1,75kg bags.