Low PH in fresh mixed salt water

[Ryan winder]

I recently got into the hobby (about 4 months now), I’ve been keeping up with my weekly water changes religiously. For the last 4 months I’ve been buying my fresh water and salt water from the the LFS. I recently purchased a new rodi unit and a box of instant ocean reef crystals. I’ve done one batch and the ph came out lower than the test kit could read. My process was 4.5 gallons of newly made rodi water followed by 3 cups of reef crystals. A small power head and a small heater set to 78 degrees mixed for 24 hour. The mixing container is a Home Depot bucket with a small notch on the edge of the lid for the cords, but otherwise sealed tightly. Why did the ph come out so low and how can I bring it up for future batches?

 

[Auto-pilot]

it could be your mix that is causing it. also the less oxygen there is in water the lower the PH will be. If you measure the PH and its low, take the lid off and put a Bubbler in it to add oxygen to the mix. If the PH raises its because the amount of distilled oxygen rose causing the PH to go up. The more CO2 the lower the PH will be and the more O2 there is the higher the PH will be.

 

[Fudsey]

Did you check the salinity of your mixed water. That ratio seems off to me. For me with reef crystals it's usually 1/2 cup per gallon.

 

[CNDReef]

Did you check the salinity of your mixed water. That ratio seems off to me. For me with reef crystals it's usually 1/2 cup per gallon.

im with fudsey on the salt quantity.
2 and a quarter cups should get you into the ballpark on 4.5 gallons

 

[Ryan winder]

I used 2.5 cups originally and the salinity was 1.023 then added 4 more tablespoons to bring it up to 1.025 so I guess I actually used 2.75 cups not three but would any of that actually affect the ph ? Also wouldn’t. 500 gph powerhead aerve the same purpose as an air stone it tumbles the surface of the water vigorously

 

[cracker]

Not if it has a tight fitting lid making it fairly water tight .Consider taking off the lid next time.

 

[Fudsey]

Try taking the lid off and letting the pump go overnight and check it in the morning. I'd bet the pH would be back up.

 

[Ryan winder]

Will do maybe I’m just being paranoid but I live in a one bedroom apartment so I’m limited to where I can mix the saltwater. Was worried about contaminates getting in there

 

[Randy Holmes-Farley Verified Community Expert]

it could be your mix that is causing it. also the less oxygen there is in water the lower the PH will be. If you measure the PH and its low, take the lid off and put a Bubbler in it to add oxygen to the mix. If the PH raises its because the amount of distilled oxygen rose causing the PH to go up. The more CO2 the lower the PH will be and the more O2 there is the higher the PH will be.

Not entirely. pH is only related to CO2. O2 has zero impact. Reefers can encounter high and low CO2 entirely independent of the O2 level.

 

[Randy Holmes-Farley Verified Community Expert]

I used 2.5 cups originally and the salinity was 1.023 then added 4 more tablespoons to bring it up to 1.025 so I guess I actually used 2.75 cups not three but would any of that actually affect the ph ? Also wouldn’t. 500 gph powerhead aerve the same purpose as an air stone it tumbles the surface of the water vigorously

At a given salinity, pH is determined mathematically (meaning exactly in a predictable way) by the carbonate alkalinity (which relates to salinity) and the CO2 level (which relates to the starting mix, or after complete aeration, to the home air CO2 level.

I generally would not worry about the salt water pH. It will only have a minor impact on the tank pH unless you are doing unusually large water changes.

 

[Ryan winder]

Thanks for the replies.i do a 15% weekly. I checked my tanks ph 2 hours after adding the water and there was no noticeable drop in salinity. Even having that peace of mind wasn’t enough though so I purchased an air stone and a small pump for the next batch to see if I could get it closer. Can’t hurt right?

Edit: no noticeable drop in ph

 

[Randy Holmes-Farley Verified Community Expert]

Thanks for the replies.i do a 15% weekly. I checked my tanks ph 2 hours after adding the water and there was no noticeable drop in salinity. Even having that peace of mind wasn’t enough though so I purchased an air stone and a small pump for the next batch to see if I could get it closer. Can’t hurt right?

Edit: no noticeable drop in ph

Actually, more aeration can lower pH, so in that sense, it can “hurt”.

 

[Ryan winder]

Uh oh I’ll do a test batch and if it’s even lower than my first batch I’ll scrap the air stone. Thanks for the heads up