This is the fourth filter I have tried for my male Betta, Jake. He lives in a 5-gallon glass tank. This filter is perfect for him. He is a bit finicky about currents, hence my adventure and determination to find the best filter for him and his environment. The first one was so strong on the lowest setting that on one side of the tank he was constantly flung away and on the other side of the tank he was being sucked in toward the filter. He did not appreciate this treatment and his mood was evident. I went through two more filters with almost the same results and then found Aquarium Co-op and Cory. I had to adjust the filter to the very lowest setting but it certainly does the trick. Jake is a happy camper now. I would rate this filter an A+ for finicky fish.
P.S. - As a side note, I have this filter in one back corner and in the other back corner I added Aquarium Co-op's small sponge filter - http://www.aquariumcoop.com/collections/filters/products/mini-fine-sponge-filter. I wasn't sure that Jake would like the sponge filter but he does! He plays in the bubbles!