The salt i have says it will keep ph at 8.3 is this right?

Will it do that keep the ph at 8.3 or shall i check the ph every week to make sure ?

 

your ph will change throughout the day depending on many factors a salt mix will not "keep" a certain ph in a tank.

 

Um.. Thats a load of %$%£%$ if you ask me. Id still check the pH now and again

 

Only a proper balance will maintaint ph. Alkalinity and Ions. Regular water changes with quality salt will maintain levels of Elements but I recommend using a buffer to maintain ALK and PH. Seachem Reef Builder works well, there are also a few 2 part solutions such as 2 little fishies C-balance or B-ionic and these will maintain Alk, Calcium and Trace elements but my experience w. C-balance is that you have to watch your magnesium levels. Also, please don't add anything without being able to test for it. Alk and PH tests are a must. Over time your tank will be more stable in controllong PH and Alk and other factors can effect PH change throughout the day such as a room w/ poor air exchange, amazing what a window can do sometimes. Good Luck

 

What it doesn't say is HOW LONG IT WILL KEEP IT AT 8.3.
Every tank is different and based on the loading, will vary as to how long before the buffers are used up and need replenishing.
pH will also vary with the gas exchange going on at the water's surface.
If the home is shut up and has high CO2 levels (as in winter for example) then the pH can be significantly lower, even if there is sufficient buffer available in the water.
Adding more buffer in such cases is unlikely to achieve a high pH, but more agitation of the surface might, and more outside air will, up to the limit of the buffers.