It is amazing to know that the sponge filter is actually producing some type of flow, but you are correct that the flow does not have to be in a uniformed direction.
Thank you for the informative information regarding sponge filters because I do not have experience with it since I use an HOB filter for my QT tank. It is amazing to know that the sponge filter is actually producing some type of flow, but you are correct that the flow does not have to be in a uniformed direction.