Translation:In one day, it must be purchased once.
I would be grateful for a real-life example of when someone would ever say this.
The sentence doesn't say that, either. In one day is not the same as once a day. If I only fed/bought it once and never again, the sentence would still be describing that.
Hoch jaj wa'logh je'nISlu' It needs to be fed once a day.
Maybe it could be reformulated as: "qaStaHvIS wa' jaj, wa'logh SopnISlu'" or, David's formulation "Hoch jaj wa'logh SopnISlu".
You're right. The sentence is in the section about passive voice, so using -moH would express correctly what was intended with the original sentence, but it wouldn't fit in the section anymore. Too bad there's not another word for "feed".