RO/DI water and pH control

[yimmit]

Hi everyone! I have a small problem and was wondering how you would deal with it. I have made some fresh sea water using Instant Ocean and RO/DI water from a Kent Marine Hi-S unit. When I test the pH, it is something like 7.4. How can I buffer it back up to 8.4? And how do I go about keeping the tank pH up since it is likely that the RO/DI water for top off will be very low pH. Thanks for any help you can provide!

Oh yeah, one other quick question: This is my first time using sand for the substrate. I have the tank filled and I can see pockets of air in the sand bed. Should I stir up the bed to eliminate the air pockets? or will the disappear on their own?

Thanks again!
Tim

 

[Anonymous]

Hi, yimmit! Welcome to reefs.org.

I would poke a chopstick or something to collapse the air pockets. As for your alkalinity, if you're using a calcareous substrate it should come up (pH as well with the buffering), but you may also want to consider using kalkwasser or one of the two part systems that add calcium and help keep the alkalinity up as well. Better to get this all sorted before you start adding anything to the tank.

 

[Len]

The bubbles in the sand is fine. Sub-substrate species will move things around, so no need to be concerned about it. In fact, there will always be some gas bubbles in the sand since a lot of byproducts of biochemical processes, like denitrification, are gaseous.

Try aerating your newly mixed water. This usually brings up the pH. If not, SW pH will naturally settle about 8.0+ over time, and isn't really shouldn't be an issue. The carbonate substrate will buffer the tank against pH drops. Like a lot of reefers here, we use RO/DI water as top off without "prepping" the water at all.

 

[yimmit]

Thanks for the replies! I didn't believe the pH test results for very long, so I went and got a better test kit. The readings from the new kit (FasTest) show a pH of roughly 8.2 - MUCH BETTER I'll probably use the OSMO Prep Marine from Kent in the top off water - at least for a while to make sure the pH doesn't drop off. The sand bed is oolitic aragamax and special grade reef sand - should be a good buffer.

I poked around a little bit along the glass to release some of the air. Considering there are well over 400 little bubbles just along the glass, I don't think it's possible to poke around to release them all. Probably would need a good stirring to get them all. I guess I'll leave them alone and hope the critters in the fauna kit from Inland Aquatics will eventually get them all. (Not to mention the stirring that will occur when adding the live rock to the system.)

Thanks again for the replies and the welcoming.

Tim

 

[Robin Goodfellow]

RO/DI water for top off will be very low pH.

hi.
pH in ultra pure water is kind of tricky to define. Even if the pH meter shows a pH of 2 in a 5 gallon of RO/DI, it only takes a single grain of salt (or a dirty hand) to change it to 7 or 8. Don't be too concern about low pH in RO/DI, and get fool into buying junks.