High Range Ph 8.4

done my weekly test to day and the only change was my ph was 8.0 the past 5weeks but now is 8.4, water change was done yesterday is that ok or what should i do?

 

If its a reef tank then thats right where you want it. Have you tested for alkalinity?

 

yes its a reef tank. no i dont think so my nitrite is 0 and my ammonia is 0 and my nitrate is between 10-15 and my hydrometer is reading 1.024. should i buy another test kit for the alkalinity

 

What are you using to test the pH? What time of day are you testing the pH? The pH will fluctuate during a 24 hour cycle due to photosynthesis in the tank. If it has been stable for 5 weeks and now went up, either you changed the time of day that you tested it, your test is wrong somehow, or something else has changed in the tank. pH is one of those things that if you keep calcium, alk and magnesium in line, the pH will take care of itself. Just don't try to use any of the pH buffer bottles they sell. They cause more problems than they solve.