Low alk and fish
 

Hello I have just tested my alk in my system and it's 5.4ppm would this low reading affect fish negatively especially wrasses? I have no corals in this tank.

Alk doesn’t effect fish. No reason to even test for it if you don’t have corals. For fish only systems I would only monitor salinity and temp.

I agree that the fish won't care about the alkalinity itself. If the alkalinity drops to a very low level, the pH might become an issue, at least in theory. I might check the pH.

You can easily bring the value up with a little baking soda, by the way.

From what I've read, having low alkalinity can make your tank more prone to large pH swings. The fish might not care about the alkalinity in itself, but I don't think large swings in pH are good for fish.