I just hooked up a RO/DI unit and the water out of it has the same PH as the water going in..Its really High like 8.8.......My question is when this water is mixed with reef salt mix will it buffer the PH to 8.2 or 8.3? If not,,what would be the recommended way to lower PH that is that High?

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Every man is guilty of all the good he didn't do.

Nevermind!!!! After it aerated for 10 minutes it dropped from 8.8 to 7. :o)

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Every man is guilty of all the good he didn't do.

If you have trouble bringing it down in the future, grab a jar of PH buffer. it will bring it down and it's safer than using a PH lower.

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36 Gallon Saltwater reef tank
Ocellaris Clown, Scooter Dragonet, sandsifter star, Decorator crab, emerald crab, coralline snails, blue leg hermit crab, and horseshoe crab.
Zooad's and shrooms
40 pounds of Live sand, 20 pounds of LR

I would recommend you delute your 8.8 RO water with Distilled water first before make your Saltwater Mix. Try a 50% mix of your RO and distilled water and see what your ph is. Mixing your 8.8 and Saltwater directly would possibly destroy the ph buffering capability of your Saltwater.

glad you remeasured.

FWIW pH is a function of carbonate and carbon dioxide. therefore the high pH was probably due to a lack of co2 and as you found out simply aerating results in pH being lowered. It can also start lower and go high.

Just depends on th co2 of the surrounding air, resulting from plant action and the initial state of the water.

my .02

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fw leiden since 1979, fo salt since 1979, mixed reef 55g 2002-2009. Strong emphasis on the tank taking care of itself. Balanced with plant life, no water changes, tap water, no filters in FW. Only dosing calcium, alk, mag in marine reef tanks. http://www.aquariumforum.com/f15/my-...ods-26410.html
recent tanks (till 2009) 7 years- 10g FW leiden 7 yrs, 55g mixed reef 7, 2 yrs, 20g FW leiden, 10 g fw leiden , 29g mixed reef, current tank 55g leiden