There isn't a simple chemical to add to lower the TA. The only thing that would do that would precipitate out carbonates and would then need to be scooped out, but I'm not aware of any such product (other than those that would cause staining like copper or that would cause scaling like excess calcium). Aeration to drive carbon dioxide out of the pool is the way to lower the TA. For greater aeration, using an air compressor with a nozzle or pipe with small holes to make small bubbles has been most effective, but the jet air fitting referred to in previous posts sounds like it might work well. I just bought one and will try it out this summer (my TA only needs to be lowered a little -- from around 130 to 80).
Richard
Richard