I use kalk in my ato, and its pretty much the only additive I add on my 75g, and works great. I have been at max saturated solution for about a year now, and as such occasionally, about once a month, have to adjust the alk a tad up, as my tank uses slightly more alk then I can put in with the kalk. Generally though my tank stays right between 410-420 calc and 7.2-8.0 alk, and doesnt waver much from that
When I started though I started with a half saturated solution and slowly worked up from there, so 1 tsp per gallon. So with you tank I would start slow, monitor your levels and adjust the solution accordingly.