Actually I didn't test GH lastly but if TDS is 250 GH is somewhere between 7-10.
Test is less than a year old.
My tap water have PH8 , TDS130 ,GH3 and ,KH3.When I mix it with RO 50/50 I need to add GH buffer.
Paraguard is OK but didn’t help much. Melafix is beter but only helps in some cases.
I haven’t used tetracycline or Erythromycin. Will the shrimps survive it?