Help! Ph 4,5 in my CRS tank.

[Andryk]

Please help. I have noticed that after every water change next day one or two shrimp die. Now I measured ph and it was 4,5. Shrimps do not feel well, they are sitting still and not move actively. I have 100L tank with Red Bee Sand and bottom filter. How I can rase my tank ph and stabilize it safe and quickly? My tank Kh-0 and Gh- 4 And TDS 130.

[wyzazz]

What are you testing your pH with?  And what are you using for remineralizing your RO water?  4.5 is very low.  Adding kH will bring your pH up, baking soda can do this pretty quickly, but I recommend making these changes slowly.