Carol how much of the crushed coral do you use per 10 gallon. Does'nt clam shells do the same as the crush coral??Butterfly said:The arm and hammer acts just like ph adjuster and can cause fluctuations and has to be added everyso often. Whereas the crushed coral substrate will raise it and keep it at the same ph without having to do anything else. i guess I'm lazy but thats too much testing, measuring and mixing for me I'd just as soon throw the substrate in and forget it.