I did an Ahh-Some treatment on my hot tub/spa today. The fourth time in 3 years. The first time cleaned out a lot of gunk. The next 2 times came out with less and less. This time virtually nothing, very little scum ring. So I must be something right as far as spa maintenance goes. We have had this Hot Springs spa 4 years. We abandoned the recommended chemicals after the first year because of poor results. TFP recommendations for the spa and my swimming pool. They work.