6.8 ph from freshly mixed salwater
 

Ever since I switched over to making water myself at home I've been having a PH/Dissolving coral issue I can't figure out.

I took a cup of freshly mixed salt to the PH probe on my apex and the probe started reading all the way down to 6.8 , this explains the disolving snail shells/corals.

I'm guessing the issue is c02?
I have 2 65g containers, like these.
https://encrypted-tbn0.gstatic.com/i...cOzmE3V0zE1FAs
I have a 1300gph powerhead inside the container, but I usually only leave it on for 30 minutes after adding salt, then afew days later when I am ready to do a water change I turn it on again.

There are alot of calcium flakes inside the salt mixing container, which I think is also indicative of ph/c02 issues.

Is adding a air pump and bubble stone going to be enough to fix my ph issue? or is my mixing container too sealed? Whats going on here?

Are you sure your probe is reading right? A ph that low would need a abnormally high ambient co2 level if it is in equilibrium with the surrounding air.

Surely your tank can't be that low or nothing would be alive very long.

The tank isn't that low, a single cup of saltwater, directly from the mixing container reads 6.8.
Strangely the tank was at 8.0ph, but after pulling out the Apex PH probe, dipping it in the cup of new salwater, and then putting it back in the tank, its now reading 7.2ph.

I don’t think 30 minutes is enough to dissolve the salt, you should keep t mixing from the time you add salt until you use it.

Can you elaborate on the “dissolving” issues you are having?


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Coral skeletons and snail shells dissolve in my tank.
Corals in general have been in decline since I started making my own water, I don't usually test my water, my philosophy has always been water changes can fix anything. But in this case more water changes seems to be making the situation worse.
I kept a log for afew months trying to figure out the issue, I realize now I was checking everything EXCEPT ph. I'm kind of dumb when it comes to water chemistry but I always thought that if I maintain cal/dkh/mag that ph would handle itself.

I'd check the alkalinity, and probably get a second opinion on it and the pH. It's largely impossible to get the pH to 6.8 if the alkalinity is in the normal range and there's even minimal aeration.

Something is up with the Apex's ph probe, since I pulled it out to test the freshly mixed saltwater its only reading 7.2 on the tank when before it was reading 8ph. Maybe some oil from my hand got on the end of the probe?

I found a really old API ph test kit and test my display, the freshly mixed salt, and my ro.

According to the old API test my RO is around 7.4, the new salt is around 7.9 and my current tank water is around 8.

And thats why no one trusts the Apex PH probe, and probably why no seasoned reefer checks, or even knows what their PH is.



PH will be what it wants to be. Throw the probe away and never look at your PH again.



If you have coral skeleton dissolving, I would be looking at my alkalinity, and/or calcium before I was worried about PH. Your PH would have to drop to a very low level before coral skeleton started to dissolve. At that level the arrogonite we use as a sandbed would start to dissolve which would bring the PH back up.

I used to test samples of my RODI in a clean plastic cup.
When I test the water in the cup versus the water in the holding tank it always differs.

Ph in the cup is 7.2 and in the holding tank 7.8
TDS in the cup is 7-10 and in the holding tank 0-1.

I have no idea why, just guessed maybe the small sample.

pH meters are prone to electrical interference, among other issues. If you want to see what's happening, I'd recommending calibrating with fresh solution and work on electrical isolation. Moving the meter and probe away from the tank, and onto a separate circuit, might be useful. The Oakton OneShot pH calibration packets seem fine, in my experience, although a bit pricier than a bottle of calibration fluid.

I need to get some new test kits to test my fresh made salt water, but I know calcium precipitating out is a big problem.
At the bottom of my mixing container I have large flakes of calcium. What would cause the calcium to precipitate out?
How would this loss of calcium affect the DKH of new batches of saltwater?
How can I stop this?

You can't measure freshly mixed saltwater, you need to wait and let it settle and equalize.

Test it 24 hours later and see what it says. (Ignoring issues with the Apex probe). It should be closer to what you expect.

Your mag is around 1350 right?
To me, it sounds like a low mag problem, CA and Alk are preciping out if water and nit available for calcification.
Low magnisum in your salt is the usual cause.
Mags job is to make the CA and Alk ions less attractive to each other, so they just don't come together and crystallize.
Some salts are cheap on the mag...

I use Red Sea salt in the blue bucket and the instructions say to wait for the PH to stabilize before adding to reef.
Cheers! Mark

A bit of buildup of calcium carbonate at the bottom of mixing containers seems fairly normal. Brands of salt that mix to a high initial pH might be more prone to that problem.

I agree that the pH can take a while to stabilize, as the carbon dioxide level in the mix equilibrates with the ambient air. I'd give a container three hours if there's a small pump running, but I've never measured the time required. The three hours is based on a pH aeration test.

Red Sea advises against mixing for more than 2 hours.

Crap sometimes i leave a batch of salt in the mixing container for weeks before actually using it.

Also I use Reef Crystals.