I used this on my tank that has alot of alge. It took care of some spots quickly. Others i needed to scrub hard. I also have a very stubbern red alge that came off with persistant scrubbing. I got 3 sponges in the pack . they measure 4.5 inches X6.3 inches. #rankboosterrevie #Sponsore #SunGrow https://www.amazon.com/SunGrow-Remove-Stubborn-crannies-easily/dp/B07214642F