I have gone through 8 rcs lately and they were fine until I added excel.This is a 16g planted tank with neon tetra and it was just the shrimp. It is newly established but from used media from my other tanks. The water parameters are 0/0/0 I know the 0 nitrates sounds funny but I have constantly tested my self and all I can put it down to is the plants. maybe I am one of the lucky ones with no trates. I want to know if anyone else has had trouble with dosing excel with shrimp.?