Neptune Aquatics

Where's my alk going in my mixing station?

R

richiev

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I've been having really weird alk issues in my saltwater mix. I'm testing it after mixing, and it has been lower then expected, let's say 8 dkh. Then I leave it for a couple days, and I'll test it again, and it'll be like 6.8 dkh.

I've added some soda ash alk liquid, diluting it even more with RO and then slowly pouring it into where the mixing pump sprays out, trying to ensure I don't precipitate. I've tested afterwards and seen a reading above 9 because I was off on my estimate (targeting 8.5). I then test it a day or two later and it's in the 7. Days later I'm at 6.7.

Red Sea black bag. pH seems about right. Salinity in the 34.5ppt range. In a brute garbage can with lid on. I haven't dumped the can recently, but I don't think I see any major precipitate on the bottom. Mixing pump is a little return pump from a fluval and a little powerhead.

Not heated. I'm pretty sure I've seen this happen both with and without the pump having ran.

Garage does get warm.

This seems very weird, I'm not sure what's going on, and it's annoying to feel I need to test my mixing water every time I want to use it.

Tested with a Hanna and my diy alk tester. Both give good readings on other setups, and I can see the numbers high after adding alk so a reading issue can't explain it.
 
Brs did a pretty good video on different salts and how fast the loose alk just sitting. Red sea was one of the worst
 
Red Sea Coral Pro instructions mention the salt should not be mixed for more than 4 hours. I think this is why reefers who store large quantities of salt use other salts.

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bp123987 said:
But….. why?
Click to expand...
Taking a wild guess, but it could be the alkalinity (e.g. carbonates) decomposing into CO2 + byproducts and the CO2 gassing off. Remembering back to O-chem, this is why carbonated beverages water down (bicarbonate = H2CO3; breaks down to H2O and CO2), so could be something similar going on with alk.
 
Interesting anecdote, I rebuilt my water mixing station, ditching the big ugly brute for a 20 gallon aquarium. Looks a lot better, I can see what's going on better, and I can even use one of those cheap stick on thermometers for an approximate temp. 9/10, wish I'd of done this originally.

The interesting alk part is now my dkh is very stable in the mixing water. Same salt, same pumps, same RODI coming in. Nothing changed in the garage/house recently. Only other thing I did was clean the pumps with citric, but they weren't that bad.

I don't know how to explain it, and it might be pure correlation, but I find it very interesting how drastic the change it was. I used to be going from around 8.5dkh to 7 or below in about a week. Now it's hardly moving at all.
 
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