Help with Chemistry Please

[VIVVIV]

Tank is fairly new but has cycled. Just did a 30% water change and it does not seem to have had much effect on the the ph and alk.
Before the change it was 7.4 and 15.3. Now after the change and letting it run for a few hours my ph is 8.4 and dkh is 15.3!

Source water before adding salt tests out at 8.6 and 7.2

Salt is at 35.

What should I do?

Thanks

 

[outssider]

your alkalinity is high because you are not using ro/di water as a source. Salt mixes are designed to be mixed with ro/di water that has an alkalinity of -0- . ph is a function of co2. you really don't need to fool with ph unless you have a gaggle of people in the house spewing out co2. If you do nothing, the alkalinity will slowly go down.

 

[dkeller_nc]

Yep, you're going to have some real alkalinity challenges if you're intending to keep coral and are using municipal tap or well water. If you're simply keeping fish, well water might be OK, but over time, even very good well or municipal water typically has trace amounts of metals such as copper that will build up in the aquarium. It might be quite a long time before that will affect fish, but it's generally deadly to invertebrates/corals.

 

[wrott]

pH is not a number you should ever chase, it's fine
As stated, alk will be high with tap water. Unless you have fast growing SPS or clams, alk and Ca will not be depleted as fast as you might think.