We need much information about your tank setup and history, but on the surface I think you may have added too many fish at once. The increased bioload would cause a spike.
How long has it been up and running with fish?
How was the tank cycled (and when)?
What are the current tank inhabitants?
Do you have any live rock? If so, how much?
How often do you do partial water changes?
How much do change at each PWC
What is your process for a PWC
(do you mix it the night before making a change?)?
What do you feed the tank?
How much at each feeding?
You must have test kits that give an exact reading (not low/high).
For Salt (SG
), any reading not taken with a calibrated refractomer is suspect.
You say your Alk
is high! We need to know just how high it is. High may be a good thing or it could be off the charts.
's are a good general cure. For now, I would suggest you prepare another 20% PWC
to help get your readings back in check.