How do you start a tank for caridina?

How do you start a tank with low tds? My tap is in 300+ range and when I use distilled and remineralize then I can get to around 150 with gH and kH in range but then after plants and fertilizers it jumps to 250-300 range. I’ve tried 3 times and all 3 times my tank ends up being in the 300 range.