Still dealing with this. Still showing Ammonium, shrimp are fine, still..and eating as usual, and being active. Nitrite spiked to .50 for some reason, today was WC change anyways on the EI schedule. So I did a solid 50% WC and all is well, except for the Ammonium reading. Not sure what else to do, I have tried adding "mulm" from my other established tanks..and just waiting it out. Also added some seachem stability to hopefully help.