Hey there ^^, what tank is best for ACF, tall aquarium or long plastic box, more info inside:

[Jenste]

Welcome to Frog Forum! Going to touch on a few of your points.

Long tanks are preferable over tall tanks. For 3 frogs you will need about 20-30 gallons (average around 75-110 liters). You could do 3 frogs in a 20 gallon long tank if properly filtered. Always best to buy a tank for their adult sizes. It is easy for situations to arise when it comes time to upgrade and having to put it off can be detrimental to their development.

Moving old water to a new tank does absolutely nothing as you cannot cycle water. You build your bacteria colony inside the filter media, with a little bit clinging to the actual filter hosing and compartments.

Don't worry about vibrations from the filter, this is a ridiculous wivestale that spread as fact. It does not feel like a jackhammer and they do absolutely fine with filtration.

You do not need to hand feed them. It is often recommend to keep your hands out of the tank as much as possible due to risk of adding contaminants into the water. Also never feed them flakes. Reptomin come in multiple sizes or just break the piece with your fingers. Bloodworms are best as a treat.

Do not house them with gravel. It comes with a high risk of impaction. Stick to smooth sand or barebottomed. You can also use tiles or very large rocks but I prefer avoiding the rocks due to risk of weight shifting and waste getting trapped underneath and fouling. With sand you hover your waterchange siphon a few centimeters over the sand and gently swirl. The waste will be sucked up and the sand will stay down. A few grains may get lifted now or then but it will often fall back down.

Temperature is important and a steady temperature is extremely important. Keep it around the mid to low 70s *F.