Low pH

[90reefer]

I have a 5 stage RO system for make-up water, the effluent is 6.5 pH. That seems pretty low to me. Does anyone know what typical RO effluent ph should be? I cannot seem to get my reef aquarium ph above 7.8, no matter how much calcium hydroxide I supplement. I would appreciate any thoughts, thanks.

 

[90reefer]

Switched to a new 90 gallon set-up 4 weeks ago. Have 20 gallon sump, 3300 gph water circulation and lots of surface aggitation. Aquarium has 4 inch "special reef grade" aragonite with plenum. Seeded gravel with 3 cups of my previous 8 year old aquarium substrate. Transfered 65 lbs live rock and 7 various leather corals. There are 3 fish and maybe about 20-30 small snails and crabs (reef janitors). Durring this start-up phase, I am running actinic lights 16 hours a day to give coraline algae a jump start. MH's are on 5 hours a day for corals. No visable algae yet except for coraline specs on glass. Water temp has been 78 - 80. I have been struggling with this ph issue since I switched tanks??? Previous tank had no issue staying around 8.3. Currently ph peaks at 7.8 and this morning before lights on...7.5. That is when I started checking into ph of supply water. Also, as far as aeration, the aquarium overflow discharge to sump is chock full of bubbles, to the point I am having micro bubbles going back into tank (large circ rate = no time to blow off). I also have an airstone in RO make-up container.

 

[90reefer]

Sorry, I forgot to mention that yes, I have checked ph with a newly calibrated PinPoint probe, Seachem test kit, and litmus paper test strip. All three test modes agree with low ph. On the subject of testing, calcium - 280, magnesium-800, and dKH-8. Along with calcium hydroxide supplemet, I just started adding magnesium. I just think the whole water chemistry is getting out of control and I fear for the inhabitants. I am considering doing massive water changes and start the cycling process over???

 

[90reefer]

After adding salt mix and aerating "RO batch water", ph is reading 8.0 for this batch mix. I will change out some water tonight and try your suggestion, thanks for responding.

 

[luc24cobra]

I had the same problem and I tried kalk, raising dkh to 12, check mag, calc, I tryed everything and nothing worked. For some reason my water wasn't crystal clear like usual so I start to run carbon in my system. It not only cleared up my water but my pH raised up to 8.2. Try running carbon and change it ever month or so. It worked for me!