Elsa,

A TA of 210 compared to 100 will increase your water balance saturation index by about 0.3 which is not huge. If you also had high CH and high pH, then you could get some scaling, but your water would likely be cloudy before that happens and you say your water is clear so you are probably fine in the sense that you certainly shouldn't panic.

The main problem with a high TA is that you will have a greater tendency to have your pH want to rise (due to outgassing of carbon dioxide) so you may need to add acid regularly if this occurs. This is because (oversimplifying a bit) TA measures the amount of "carbonation" your pool has and as you know from seeing carbonated drinks, they tend to lose their "fizz" over time. What you may not have known is that they rise in pH as well (though they start out at a rather low pH).

JohnT was right on with his advice so either just keep your pH down and continually add acid to keep it down or, if you want to accelerate the process, follow the link he gave to Ben's procedure for lowering alkalinity.

Richard