Hi! I haven't kept Cane Toads(as much as I wish I could), but I have woodhouse's toads, and I know what you mean about them being bottomless holes. Generally people feed adult frogs and toads every 2-3 days, and I see a lot of people recommend adding the food items, giving the toad(s) 10-15 minutes(sometimes 20) to eat, and then removing the leftovers. Personally I usually just keep to the every 2-3 days thing and give them an estimate of what I think they need. This gets easier after seeing how much they eat in that 10-20 minute time period. After observing them a few times with each food item you start to get a better appreciation for how much food they need. I wish I had more specific info for you, but I hope this helps.