If you do approx. 30% water changes per month, it really makes no difference if you use the epsom or MgCl. I did that for about 1-1/2 years with no issues. I still am doing 32 gallons per week(occationally 2 weeks) on 235 total system volume which is over 50% a month, but I was in the mood to order the correct balanced type one day so I ordered it.