u/Hot-Interest-7554

Hi guys! Just moved into a new place with hard water and I’ve been doing my best to get it under control. The toilet emits the icky hard water smell and I’m trying to be rid of that. I’ve cleaned the bowl the best I could but opened the tank to find this. What’s the best way to clean this? If this is the wrong page to post let me know. Thanks in advance. (I’ve used iron out an clr in the bowl but not sure if those are okay to use in tank.)