Alkalinity rising without dosing... possible causes?

[rynosreef]

Over the past month or 2 I've been experiencing the very strange phenomenon of my alk rising without me dosing it. I have a theory as to why that I'd like to run past you all.

I reintroduced a decent amount of sand that had been siphoned out of my tank from a while back, that was stored damp and loosely enclosed. I'm wondering if during that storage time the pH in the bucket dropped enough to partially dissolve the sand. I did rinse the sand thoroughly before reintroducing it, but maybe it's releasing carbonate in the water now that it's been reintroduced.

Does this sound like it could be the cause?

 

[Bosreef]

Have you performed warerchanges in those 2 months?

 

[rynosreef]

A little tank background: Up and running for approximately 2 years. SPS and other corals are doing fine, and are still encrusting/growing etc. So they're uptaking some of the alk that is being mysteriously introduced. I make my own saltwater using an RODI unit. I was dosing 2 part consistently before this started happening, but have now stopped. In the course of a month or so my alk rose from 8.6 to 10.2 without me dosing.

I've also noticed it's hard to keep detectable nitrate and phosphate levels. It's 25g tank with 2 fish fed 2 times a day. So I've removed GFO, cut down on water changes, increased feeding, etc. But still... my levels reach 0 within a day or 2 (testing with Hanna Phosphate Checker/Nyos Nitrate). I'm thinking the added surface area of the sand is also responsible for keeping the nutrients low and least until things balance out.

In my quest to figure out the cause of the alk rising, I have:
1. Verified my testing results with the Hanna Checker and Salifert.
2. Made sure my water changes weren't the culprit. My new salt water is 7.7dkH. I keep my tank at 8.6.
3. Completely removed the dosing lines from tank in case they were somehow dripping, wicking, etc. I only dose aminos.
4. Removed ceramic bio bricks in case they were breaking down
5. Replaced all of my RODI filters in case trace amounts of carbonate was getting through.
6. Verified my pH is in the proper range between 8 and 8.3.
7. Inspected every square inch of the tank for anything that dropped in.

My plan is to do small water changes as necessary with lowered alk to keep the it in a stable range, and wait for the sand to eventually stop releasing carbonate and for the overall system to stabilize.

Does my theory sound plausible? Any other things I could be overlooking?

 

[rynosreef]

Have you performed warerchanges in those 2 months?

Hey Bosreef! I just posted a follow-up that has more background info.

 

[Bosreef]

Above my knowledge level so watchinh along with you, thought you were just introducing the alk with waterchanges and over looking that.

One test though might be to mix up a fresh batch of saltwater, test alk, place some sand from your tank into the bucket wait then test alk.

 

[rynosreef]

That's a good idea. Maybe one bucket with no sand, one bucket with sand just to be sure.

 

[Randy Holmes-Farley Verified Community Expert]

Over the past month or 2 I've been experiencing the very strange phenomenon of my alk rising without me dosing it. I have a theory as to why that I'd like to run past you all.

I reintroduced a decent amount of sand that had been siphoned out of my tank from a while back, that was stored damp and loosely enclosed. I'm wondering if during that storage time the pH in the bucket dropped enough to partially dissolve the sand. I did rinse the sand thoroughly before reintroducing it, but maybe it's releasing carbonate in the water now that it's been reintroduced.

Does this sound like it could be the cause?

I don’t think that can be a cause of alk release from rinsed sand.

 

[Randy Holmes-Farley Verified Community Expert]

Sand and rock will slowly dissolve in low pH regions. Long time reefers need to replace sand. Is that the cause? Maybe, if the demand is otherwise very low.

Are you dosing nitrate or amino acids or anything else? These can impact alkalinity.

 

[jeffmr4]

Do you put anything in your top off water like kalk?

 

[rynosreef]

The only thing I dose now is coralAmino from Brightwell and sometimes Red Sea Reef Energy. My demand is quite low as the tank only has about 10 or so acro frags and a medium sized monti cap. My tank pH is in the normal range (8-8.3). At the deepest the sand is maaybe 1.5 to 2 inches.

I’ve been trying to methodically eliminate possibilities and must admit I am stumped...

 

[rynosreef]

Do you put anything in your top off water like kalk?

Nope. Just RODI water.

 

[rynosreef]

I don’t think that can be a cause of alk release from rinsed sand.

So you’re thinking that even if stored sand had partially dissolved from low pH, the process of rinsing it would keep it from releasing carbonate when reintroduced?

 

[Randy Holmes-Farley Verified Community Expert]

So you’re thinking that even if stored sand had partially dissolved from low pH, the process of rinsing it would keep it from releasing carbonate when reintroduced?

definitely. Anything that dissolved easily rinses away.

 

[Randy Holmes-Farley Verified Community Expert]

Depending on how they formulate it, and what happens to it after dosing (incorporation into tissue vs metabolized) the coral amino may boost alkalinity. Metabolized sodium aspartate will boost alkalinity, for example.

 

[Randy Holmes-Farley Verified Community Expert]

Same comment applies to Red Sea Reef Energy B.

 

[rynosreef]

Same comment applies to Red Sea Reef Energy B.

Interesting! I'll hold off dosing for a week and see if that changes things. Hopefully that's it! The daily increase is very small. Something like 0.056dkH. But on a long enough timeline it starts to add up.

 

[sgrosenb]

Hi @rynosreef just wondering if you have an update on this at all? I too have increasing (or non-decreasing) alkalinity. Difference for me is that my corals are just flat-out not growing. They're not dying (yet), but they're not growing or encrusting.

 

[rynosreef]

Hey @sgrosenb,

Yes! I've been meaning to update this thread. I'm not sure by what mechanism it was happening but somehow my sand was the root cause of the alkalinity constantly rising. After struggling to lower my alk and keep from constantly rising for weeks, I decided to remove the sand. Since that day my alk has stopped rising and I'm back to dosing 2 part to keep up.

The rising alk got to be such a problem that I needed to do water changes with artificially lowered alk (using muriatic acid) to keep it from rising to dangerous levels. So I'd do several 10% water changes with new saltwater with 5dkH over several days to slowly bring it down. The muriatic acid was mixed in for 24 hours with aggressive flow so the pH would be normalized before using it. However these water changes only seemed to exacerbate the problem, and despite the water changes initially working, the alk would rebound up again more aggressively.

I wish I could explain why it was the case. Perhaps the relationship between nitrate and alkalinity had something to do with it, although usually it's balanced as I understand it. I'm really not sure. But in my case at least, it was the sand.

 

[sgrosenb]

@rynosreef That is exactly what I experienced (and still do). I would do a water change, which would bring my alk down, but then it almost seemed like it more aggressively increased after the water change. So odd... There is another thread on here that I've been going back and forth with @Randy Holmes-Farley and a few others that had the same problem. They removed their sand and both had the problem go away. I have removed about 75% of my sand but there is still some sand that remains. I'm thinking I should probably just remove it all. My alkalinity no longer rises, but it doesn't drop at all either.

How are your SPS doing? I am having trouble getting my SPS to grow. After removing 75% of my sand and replacing my original dead rock with 100% live rock, I have been able to keep them alive for the last few months, but there is almost zero growth in my SPS. It seems to me they are getting irritated somehow and I can't figure it out. More background on my tank here - the thread got pretty offtrack after while, but my initial post shows where I'm at. Just curious if you see anything similar that you experience in your tank. Thanks for the look.

 

[Randy Holmes-Farley Verified Community Expert]

Very slow dissolution of aragonite from low pH in the sand/rock interior is not unexpected, and your demand is just not high enough to offset it.

This dissolution certainly happens. Long time reefers often need to add more sand to replace loses, but it is slow.