Pool Tile has Calcium Deposits

What Not To Do
1.) Do not use pumice on your pool tile, EVER. You will destroy the glazing, you will cause the calcium deposits to return twice as quickly. You will prevent any other method of calcium removal from being effective without severe risk of removing all coloration from the tile. You will, in effect, RUIN YOUR TILE. Even if you attempt to use something else to "help loosen" the calcium deposits, DO NOT USE PUMICE, EVER!
2.) Do not bother with coatings or chemicals to try and remove or loosen calcium deposits. Why? Because every year I get chemical companies who want me to try the latest and greatest, loosens and removes tile calcium and keeps it off the tile, products. Every year I state, if your company still offers these products in 5 years, and the others I talk to say that it does as is claimed on the label. It has been 30 years. Not one product is recommended. Not one product works economically. The best products require you to drain down your pool every 2 months, below the tile, get in the pool, and paint a coating on the surface. The problem, $80 per application, just in costs of materials. Add in 1 1/2 hrs. per application, and keeping cleaned tile clean will cost you $230 every 2-3 months, or about $1000 a year. You still need to drain and refill your pool every year. When the next method will do a superior job, for about $300, my suggestion is that you do not throw your money away.
3.) This leaves glass beading, wire brushes, ... I do not recommend high speed wire brushes. The wires break down during the process, sometimes they rust on the pool surface, or get stuck in the swimmers feet, even months later. Some things to think about with regards to glass beading:
    a.) I do recommend glass beading by a company that has a few years experience with the process.
       i.)  It is far too easy to get the pressure, or feed rate wrong and remove the coloring on tile to let someone inexperienced work on it.
    b.) Even when the tile is in good shape, and the cleaner knows what he is doing, there are some things to be aware of:
              i.)  Some tile is made of natural slate or stone. There is no way to avoid some discoloration of the stone or slate surface. Likewise, natural stone water features will also discolor with the removal of deposits, but most of the time the effect can be minimized by blending, or feathering, the application area into non calcified areas.
              ii.) Faux rock water features CANNOT BE CLEANED WITHOUT REMOVING THE COLORATION. You will need to have the color treatment reapplied by a company that specializes in faux rock water features after the deposits are removed.
              iii.) All experienced glass beading companies will start in an area that is less noticeable, i.e. closest to the house, away from the steps or the skimmer, ... to test for color fastness, proper pressure, ... That said, there is no way to guarantee that all tile is in the same condition, and there is no way to know if the previous owner may not have used pumice, or if the previous tile cleaner may not have damaged the tile in a few unknown areas. This is the reason for release forms. Understand that your tile cleaner cannot be responsible for damage already present. That said, a reputable company will stop the process and ask for your opinion as to weather or not they should continue, and point out the damage when they see it. Already damaged tile will get worse with each subsequent cleaning.
It can't be done. All you can do is limit the buildup. If you remove calcium from the water completely, it will leach it out of the pool surface and it will crumble into the pool.
Limiting Calcium Buildup
1.) Drain and refill your pool every year (Click Here)
2.) After getting your pool cleaned, lower the water leveler to a point where it "Barely" prevents your skimmer from sucking air. Then, when you start noticing a calcium build up, raise the water level 1/16 of an inch. Whalla, calcium deposits "appear" gone. You are already paying the tile cleaner for cleaning the entire tile, why not use more of it before you have to call him in again. Regular draining (See #1 above) will greatly lessen both the amount of deposits, and the rate of deposition of the deposits on your tile. Not doing regular drains can result in you getting the same amount of deposits in one month as that of a pool drained properly, and on schedule, gets in one year.