Odd drop in Alkalinity

[dangros]

Why am I seeing such a low measure of Alk? I measured it at 5.6 today.

The Alk was struggling to stay over 7 the last 2-3 weeks. Last year, I had to watch things or the Alk would jump over 10! I'm running a calcium reactor AND a Kalk reactor so this really made me scratch my head. I've never seen it that low, so I replaced the battery in my Hanna checker and tried again. STILL 5.6.
Could I be overdoing it w/kalkwasser and a calcium reactor??

Everything else seems great:
Calcium 470 (which is higher than my usual 420 or so)
Mg 1600
pH ranges b/w 7.9 and 8.2+
Phosphates .03 ppm

Luckily, I did a Triton test and am waiting for the results. Should be any day.

The corals look good and the only sign I see of any potential issue is some browning in the coralline algae... but this tends to happen when I need to replace my spectrapure filters. It's been about 3 months and I have some waiting to arrive as well.

 

[Randy Holmes-Farley]

I don't think overdoing it is the likely explanation. More likely not keeping up. Corals grow, reactor media depletes, etc.

 

[dangros]

But I only have a 90g tank. There's not a ton of SPS and none of it is huge. There's a good bit of coralline on the tank walls and rocks but I would think the reactor alone should be able to keep up (Geos 612). I just changed the media out less than a month ago so that's full.
Once or twice a week, I've been putting Kalk in the top off water and the in the Kalk reactor as well.

 

[Randy Holmes-Farley]

Your test may certainly be off for some reason and the alk is higher than you think, but without a measurement of how much alk you are delivering each day from the reactor (by the alk in the effluent and the volume it delivers each day), its hard to say if it is adequate, inadequate, etc.

 

[dangros]

So it turns out that the alk was very low. Not sure what’s up with the reactor. Maybe the media is too large (Arm extra course)? I used baking soda to slowly raise it to 7+. Thanks for the baking formula @Randy Holmes-Farley. Last week, I dropped the effluent drip rate to approximately 30ml/min and the pH in the reactor to 6.5-6.52. I was surprised that it didn’t seem to raise the Alk.
Unfortunately, I am away from home for a few days. I really hope it doesn’t plummet again. I put a few table spoons of baking soda in the ATO reservoir hoping to at least hold it off till I return.
Dosing alk and calcium manually is starting to look more appealing.

 

[Randy Holmes-Farley]

When you are back, if you measure the alkalinity in the effluent of the reactor, and its flow rate, we can assess how it is doing.

 

[dangros]

I'm back from vacation and the tank looks great (minus the slight algae on the glass). It's funny how going away is either the best or worst thing for you tank !
So, I just measured the Alk of the effluent using Hanna's Alk checker. It is 11.7dKH and dripping out at 34 ml/min. The tank's current Alk is currently 6.6dKH. Does this add up?
Here's a pic of the calcium reactor and the amt of media, which is filled to about 2 1/2 inches from the top.

 

[Randy Holmes-Farley]

Do you know how much volume flows out of the reactor each day?

 

[dangros]

I’m not sure outside of the effluent dripping out at 34ml/min. It’s fed by an MJ1200 and whatever is the standard sicce geo puts in the 612 reactor.

 

[Randy Holmes-Farley]

I’m not sure outside of the effluent dripping out at 34ml/min.

That's what I meant. Sorry, I missed it earlier.

The alkalinity in the effluent can certainly be raised quite a lot, if needed, by adding more CO2.

Right now you are effectively delivering 11.7-6.6 dKH = 5.1 dKH, and at 34 mL/min, that's 49 L per day.

In a 90 gallon total volume tank, you are adding 49/90 x 5.1 dKH = 2.8 dKH per day.

That's a reasonable amount, but not high.

If you want alk higher, I'd add a bit more CO2 to the reactor.

 

[dangros]

Scratching my head b/c the pH in my reactor is maintained between 6.51 and 6.53 by my Apex. I read, 6.50 is the lowest you want to go w/Arm media. It's extra course if that matters.

 

[Randy Holmes-Farley]

Scratching my head b/c the pH in my reactor is maintained between 6.51 and 6.53 by my Apex. I read, 6.50 is the lowest you want to go w/Arm media. It's extra course if that matters.

Well, I have no experience with that reactor or that media, but many reactor/media combos are able to put out 30 dKH in the effluent.

 

[dangros]

That's quite a difference. I just moved the pH probe up and added some more media. I also increased the effluent rate to 48 ml/min.
The Alk measured at 12.6 dKH now. Lets see how much of a difference this makes over time.
Btw, I have a 40g sump so when I calculate water volume, I usually go w/a conservative 100g (subtracting stuff in the tank and sump).
Thanks for the input Randy. It's always nice to see you so active on the boards.

 

[Randy Holmes-Farley]

Thanks and good luck!

Happy Reefing.

 

[dangros]

It seems the adjustments I made were not enough so I made more
I changed out the extra course ARM media to course. That gave me a slight bump w/the added surface area but it did not suffice. So I added Kalk to the top off. That worked so I stopped worrying about it and stayed the course. I've recently decided that I need to obsess more about my tank so I'm going to start looking into this again.

My plan:
1) Measure the current output of alk to get a baseline.
2) Since it's been a while, it's time to take apart the reactor, clean it and it's pumps, then add more media (Caribsea ARM course)
3) Ensure that all air and water hoses still have a tight connection. Hoses do get rigid over time and may need replacing.
4) Pull one of my canisters off an old rodi unit and turn it into a 2nd chamber w/ARM regular media
5) re-measure and hope for the best.
I've seen people with bigger tanks use this reactor so something must be wrong if it cant keep up.
@d2mini, how's your Geo 612 doing?

 

[d2mini]

@d2mini, how's your Geo 612 doing?

Love having a CaRx again, but have had some issues with the Geo.
https://www.reef2reef.com/threads/frustrated-with-my-geo-calcium-reactor.421124/
It's running ok now though.

 

[dangros]

I hear you d2! After a very late night taking everything apart on the 612, I cleaned and reassembled. As I did, I noticed the bottom 2 union screws (holding the pump to the reactor's bottom) were a hair loose. That gave me hope that a good cleaning, tightening, and media refill would improve the output of the reactor. It didnt! I got pretty much the same values after measuring the effluent. (~12 dKH @ 42 ml/min).
The next morning, I noticed a black o-ring about 2" in diameter laying by the sink where I had worked on the reactor. I was not sure where it belonged but I had to get to work so I put it aside and left. When I returned, the o-ring had vanished. dang babysitter cleaned it up so it's lost.
I emailed Geo but no response. Frustrating.
I feel a bit defeated. It's possible the reactor isnt getting enough circulation due to the o-ring missing but 1) I'm not 100% certain it belongs to the reactor and 2) it seems to be working fine. But it's certainly not putting out enough alk and calcium to keep up w/the tank.
Here's a crappy fts to give you an idea of the amount of corals in this 90g tank. I wouldnt say that's a huge amount but apparently it's more than this 612 can handle. And yes, that's an H. Magnifica (Ritteri) which decided to climb up on the front glass!
Tonight, I made a 2nd chamber out of an old RODI canister and insert I had laying around. It's filled w/ARM regular which is about the size of gravel so there should be tons of surface area. Real curious if this has any impact on pH or dKH. I'm open to any suggestions.

 

[dangros]

Preliminary results looked better this am. pH was slightly better compared to recent night cycles but that could be due to other factors. More importantly, the alk moved up almost 0.5 dKH.
I’ll check again tomorrow.

 

[dangros]

Sadly this isnt bumping it up enough. I cant help but think something is wrong when a Geos 612 cant keep up w/a 90g tank

 

[MnFish1]

Why am I seeing such a low measure of Alk? I measured it at 5.6 today.

The Alk was struggling to stay over 7 the last 2-3 weeks. Last year, I had to watch things or the Alk would jump over 10! I'm running a calcium reactor AND a Kalk reactor so this really made me scratch my head. I've never seen it that low, so I replaced the battery in my Hanna checker and tried again. STILL 5.6.
Could I be overdoing it w/kalkwasser and a calcium reactor??

Everything else seems great:
Calcium 470 (which is higher than my usual 420 or so)
Mg 1600
pH ranges b/w 7.9 and 8.2+
Phosphates .03 ppm

Luckily, I did a Triton test and am waiting for the results. Should be any day.

The corals look good and the only sign I see of any potential issue is some browning in the coralline algae... but this tends to happen when I need to replace my spectrapure filters. It's been about 3 months and I have some waiting to arrive as well.

Does Triton measure alkalinity?