Salt mix PH

[Cole_BB]

Ok so the ph coming directly out of my r.o. system is somewhere between 6.85 - 6.9 and my reserve tank from the sysem has been testing at about 7.5 normal for that to rise??
I have way overkill aeration and circulation in there...
Also after i mix my salt ..reef crystals.. in there my ph goes to 8.25 for a minute or so then drops to 7.8.. my alk for my r.o. is zero.
and yes my ph monitor is correctly calibrated..i was hoping it wasnt
any advice???

 

[Kurt_Nelson]

Only advice I have is that testing RO water for pH is not really going to tell you anything. Assuming the RO water is pure, from my understanding (I'm no chemist), pH will be meaningless because any minute trace of anything will make a wild swing one way or another. I'm sure I haven't got that quite right, and a REAL chemist will correct me soon... but from what I've been taught it's really an exercise in futility.

I only trust pH readings of mixed salt after it's been mixed for 12-24 hours or so. Yes... your initial pH readings should be high, but then after a few hours should drop down a bit. I mix Reef Crystals to 1.025 with DI water and get around 8.2-8.0 for my pH after 24 hours of mixing, for what it's worth.

 

[krisfal]

Ok so the ph coming directly out of my r.o. system is somewhere between 6.85 - 6.9 and my reserve tank from the sysem has been testing at about 7.5 normal for that to rise??
I have way overkill aeration and circulation in there...

My understanding is that carbon dioxide lowers the ph of water. As that water sits (especially if it is circulating) the carbon dioxide level will become lower and your ph will rise. When I mix salt I usually let it mix for several days and this helps get the ph up. I believe I have a lot of carbon dioxide in my well water since it wipes out a DI membrane in about 4 weeks.