i just got a 35 gallon tank with a 10" fireside oscar, a pink convict, and some sort of catfish for 20$. its an awsome deal but i cant believe this oscar lived in such a small filthy tank. the gravel is very dirty you can barely see through the glass. im getting a new 75 gallon soon for my new oscar and im gona totally clean up this 35 tank and the gravel, this oscar is gona have alot better life from now on. but i was wondering what i can use to remove the calcium mineral staining in the tank from the hard alkaline water. i have tried using a my aquarium brush, and a scotch brite pad but you know how hard this stuff is to clean off the glass. so is there anything around the house to use or some kind of aquarium cleaning product stong enough to clean this stuff off?