Is Alk usage variable?

[Bill_Moorman]

Like many of us, I test and dose alk daily. I notice my numbers vary day to day. It could be margin of error in the kits (Hanna) as well as dosing. For example, BRS calculator has me adding 5.7 ml of alk to go from 8.8 (this mornings reading) to 9.0, but i can’t accurately add 5.7ml, so I add 6ml.

Sometimes I use .3dKH in a day, others more or less.

More would make sense as corals are growing and coralline is staring to grow, but some days it uses less.

Has anyone experienced this? As I am getting closer to an Apex and dosing pumps to automate the process, I am concerned about over/under dosing as my numbers seem to vary day to day.

 

[ihavecrabs]

This is pretty normal. Most people will test daily, then every few days.. as things stabilize they'll test less frequently. However, when you have a big algae bloom, add new corals, change lighting, etc you'll need to begin testing more frequently to make those corrections as alk consumption will certaily change.

There are a few newer systems out there that monitor alkalinity and then automatically dose to correct. They range anywhere from $600-1000+ which is great insurance if you have a tank full of SPS.

Most people settle with weekly testing while things are stable and increasing frequency when they are not. Dosing systems are a must to keep things stable IMO.

 

[LobsterOfJustice]

Are you testing at the same time every day?

Between the kit itself and human inconsistency and interpretation of the results, I think 0.3 dkh is within the margin of error on most kits. You shouldn’t really see demand varying day to day (assuming other parameters like lighting are consistent) but your alkalinity will rise and fall throughout the day.

 

[Randy Holmes-Farley Verified Community Expert]

Like many of us, I test and dose alk daily. I notice my numbers vary day to day. It could be margin of error in the kits (Hanna) as well as dosing. For example, BRS calculator has me adding 5.7 ml of alk to go from 8.8 (this mornings reading) to 9.0, but i can’t accurately add 5.7ml, so I add 6ml.

Sometimes I use .3dKH in a day, others more or less.

More would make sense as corals are growing and coralline is staring to grow, but some days it uses less.

Has anyone experienced this? As I am getting closer to an Apex and dosing pumps to automate the process, I am concerned about over/under dosing as my numbers seem to vary day to day.

There certainly can be variability due to changes such as pH and possibly other factors, but if your variability is that small, kit variation/error is also likely a big part of it.

 

[Bill_Moorman]

Thanks all for the replies. I test at the same time each night. I dose alk at night to maintain a stable pH.

I just notice that some days I have a tested alk of 8.4, others 8.8, and some 8.5. No WC between those variances, but now that I think about it perhaps my “rounding up” of soda ash leaves the post test alk higher than 9.0.

 

[ihavecrabs]

Depending on what your coral goal is, you may want to invest in an automatic doser to dose over the night or 24 hours to maintain a more stable ph and alkalinity. Some corals will not appreciate the immediate .5-.7 jump in dkh while others will not care at all. Like I said, it all depends on what your goal is.

 

[Bill_Moorman]

Depending on what your coral goal is, you may want to invest in an automatic doser to dose over the night or 24 hours to maintain a more stable ph and alkalinity. Some corals will not appreciate the immediate .5-.7 jump in dkh while others will not care at all. Like I said, it all depends on what your goal is.

Makes sense. I’m only seeing a .3 daily drop, and everything seems to be thriving. As I mentioned in my OP, I am about to buy an Apex and some dosing pumps to even out dosing through the day to maintain a more consistent level.

Honestly I don’t even measure pH often, the whole chasing numbers deal causes me more stress than anything. I know it fluctuates a bit, but with the health of everything doing well, I don’t worry about it too much.

 

[Dennis Cartier]

Lets see if this works (embedding a screen capture).

This is an example of the graph from one of the automatic alk monitors that the other poster was describing. This particular one is from the Alkatronic on my frag tank. I currently have it testing every 4 hours, and you can see the daily ups and downs of the alkalinity. I dose kalk evenly throughout the day (though I am considering moving the early morning dose(s) to later in the day where demand is higher to smooth out the line). The measurements occur each day at 2 AM, 6 AM, 10 AM, 2 PM, 6 PM and 10 PM.

I am hoping to use data such as this to assist in determining if additive changes are positive or negative. My presumption is that increasing alk demand is as a result of more coral growth activity.

Dennis

 

[Bill_Moorman]

Lets see if this works (embedding a screen capture).

This is an example of the graph from one of the automatic alk monitors that the other poster was describing. This particular one is from the Alkatronic on my frag tank. I currently have it testing every 4 hours, and you can see the daily ups and downs of the alkalinity. I dose kalk evenly throughout the day (though I am considering moving the early morning dose(s) to later in the day where demand is higher to smooth out the line). The measurements occur each day at 2 AM, 6 AM, 10 AM, 2 PM, 6 PM and 10 PM.

I am hoping to use data such as this to assist in determining if additive changes are positive or negative. My presumption is that increasing alk demand is as a result of more coral growth activity.

Dennis

Works great.

So what I read from your graph is that alk does vary day to day. Even testing at the same time each day doesn’t 100% result in a consistent measurement.

Is this why literature always eludes to a “range” when discussing alk, calc and mag?

 

[Dennis Cartier]

Works great.

So what I read from your graph is that alk does vary day to day. Even testing at the same time each day doesn’t 100% result in a consistent measurement.

Is this why literature always eludes to a “range” when discussing alk, calc and mag?

Sort of. When I look at the graph, and more specifically the history, the same time each day, when compared day to day, is pretty consistent. The 30 day graph from my unit is below (with as much history as I could fit onscreen).

The daily pattern that I see, is a repeating wave, that I trace back to the light period for my DT and fuge. My DT lights come on at 11 AM (right after the highest measurement of the day @ 10AM) and have ramped down by 10 PM (where the alk is now reversing course and rising). As the fuge gets waking up, the alk starts to drop, and then starts to rise again on its way to 10 AM (the highest point of the day). Right now my fuge is pulling most of my nitrate from the water column (NO3 = 0.2). I plan to cut the chaeto back severely and see if the alkalinity demand alters during the (fuge) lit portion of the cycle.

Ah, that just gave me an idea. I am going to bump up the T5 on portion of my (hybrid) light pattern by 1/2 hour to see if the low point of the day (6 PM) also alters. This also goes to your question on the "range" that is often mentioned when discussing alkalinity. The lighting pattern/period is what drives the range. Well that along with your alkalinity additions.

Dennis