The main reason for filtration in any tank is to keep the water clean of waste and larger food particles. the filtration traps the larger particles that float free in the tank. With good filtration most fish and plant waste is picked up and removed. The other part of filtration is to insure a Bio filtration system that maintains the bacteria home that allows toxic ammonia to be broken down into Nitrite and nitrates . The nitrite is broken down into usable Nitrate for plants to feed on.
So I can only say that a non filtered tank has no way to cycle and maintain water parameters without having to change larger quantities of water per week or every other day. It's up to the individual on how much time they want to spend on tank maintenance.
Me for one I'm lazy and want to have more time spent on watching my fish instead of doing water changes. If there is no fish in the tank and it's just a Nano Planted tank then no filtration would be needed.
