What can cause occasional alk spikes or drops?

Reefs and Geeks

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I noticed yesterday a sudden upward trend in my alk which prompted me to turn off my doser for about half of the day to keep alk in normal range. My alk is normally very stable, but in the past (before adding a trident) I'd test weekly and always get crazy consistant alk results, like 9.8 +/-0.2 for a dozen readings in a row. Then out of nowhere I'd get a reading of 11.5 and spend the next week or two doing daily tests and slowly dropping it back to normal with reduced dosing.

Now that I've had a trident for a little while, I'm seeing similar results. My alk is very consistant (at least at the same time of day) day in and day out, but every few weeks or so it seems that my alk will just start rising continuously for a day or so for no apparent reason. Is this something other people see as well? Is it likely a biological function where some tank parameter just causes coral to stop calcifying for a period, or is it more likely an equipment issue where a doser will suddenly dose more than it should?

With the trident, I can now catch these spikes early and prevent the alk from spiking so high, but am still curious as to what could be causing them in the first place.

alk spike.PNG
 
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Randy Holmes-Farley

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So to be clear, the effect is not perhaps an alk spike per se, but reduced demand by corals and such that leads to a rise due to "overdosing" relative to the demand?

That can happen for many reasons, and may also be test error. Don't assume machines are perfect.

A drop in pH can reduce demand, as can something irritating the corals.
 

ScottB

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Apologize in advance @Randy Holmes-Farley but I seem to recall you posting once images and descriptions of your old and VERY reliable float switch /solenoid combination that has served you well. From visually memory, I think I have found the very distinctive float valve (Carr McMaster) but the solenoid model escapes me. Something like 120 or 1200?

Also sorry if this is a case of mistaken identity. A bit tired from all the 4am mopping up from a fail open valve and solenoid.
 
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So to be clear, the effect is not perhaps an alk spike per se, but reduced demand by corals and such that leads to a rise due to "overdosing" relative to the demand?

That can happen for many reasons, and may also be test error. Don't assume machines are perfect.

A drop in pH can reduce demand, as can something irritating the corals.
Yes, that is what I believe is happening. I don't have any reason to believe there is extra alk supplement being dosed into the tank, though it is possible as you have mentioned machines aren't perfect. I suspect a drop in demand more so because it seems the demand for alkalinity will drop off for as much as a couple of days. A bit hard to separate cause and effect since if the alk did spike, the coral could be irritated and consume less making the problem worse.
 
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Seasonal change in PH
Could be. My apex pH probe has read pretty consistent now with what I have had in the winter through. Peaks around 8.1 and daily dips at night to about 7.9-8.0. I do scrub CO2 at the air intake of one of my skimmers, though I'm not religious about changing out the media. I will change it once I see tank pH starts to trend down and it usually fixes it up. Planning to switch to just pulling outside air soon.

I just bought a cO2 monitor so I can correlate indoor cO2 levels with tank pH to some degree, and so I can see the difference between indoor and outdoor CO2 to guess how effective switching to outside air instead of a co2 scrubber. Crazy how high c02 can get by just being in a room vs the room being empty. For my early data gathering, my home co2 levels for an empty room hover around 650ppm, but a room with people in it tends to hang around 900-1000ppm. I don't ever open my windows, so it doesn't change too much, though I can now start gathering some data to prove that.
 
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Apologize in advance @Randy Holmes-Farley but I seem to recall you posting once images and descriptions of your old and VERY reliable float switch /solenoid combination that has served you well. From visually memory, I think I have found the very distinctive float valve (Carr McMaster) but the solenoid model escapes me. Something like 120 or 1200?

Also sorry if this is a case of mistaken identity. A bit tired from all the 4am mopping up from a fail open valve and solenoid.
Interesting thing about a setup with a backup fail safe is it can be quite difficult to tell when one of the devices has failed since the system would function fine if the other device is working properly. The redundancy in this case is only useful if you periodically check the functionality of each individual device. For instance, the float valve may have been faulty for many months, and you'd never know if the solenoid was working properly. But as soon as the solenoid fails, you have a flood.
 

Randy Holmes-Farley

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Apologize in advance @Randy Holmes-Farley but I seem to recall you posting once images and descriptions of your old and VERY reliable float switch /solenoid combination that has served you well. From visually memory, I think I have found the very distinctive float valve (Carr McMaster) but the solenoid model escapes me. Something like 120 or 1200?

Also sorry if this is a case of mistaken identity. A bit tired from all the 4am mopping up from a fail open valve and solenoid.

Float switch Omega Engineering LV-1201:


i never used a solenoid with it. I did use a solenoid with a tap water cooling system and temperature controller I was very happy with. I'll post it later. I still have it attached to my cold water line in the basement.
 

ScottB

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Interesting thing about a setup with a backup fail safe is it can be quite difficult to tell when one of the devices has failed since the system would function fine if the other device is working properly. The redundancy in this case is only useful if you periodically check the functionality of each individual device. For instance, the float valve may have been faulty for many months, and you'd never know if the solenoid was working properly. But as soon as the solenoid fails, you have a flood.
I totally get your point. In this case the solenoid failed closed, so I knew it was busted and had to remove it a week or so ago to keep top off running. The control fob indicated it was open but my starving pump told me otherwise.

However, had it failed open, I would only have known when it was too late.
 

Randy Holmes-Farley

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Apologize in advance @Randy Holmes-Farley but I seem to recall you posting once images and descriptions of your old and VERY reliable float switch /solenoid combination that has served you well. From visually memory, I think I have found the very distinctive float valve (Carr McMaster) but the solenoid model escapes me. Something like 120 or 1200?

Also sorry if this is a case of mistaken identity. A bit tired from all the 4am mopping up from a fail open valve and solenoid.

The solenoid I used for my cooling system is no longer available, apparently. It was a 18VA SOLENOID VALVE COIL 7TUN TYPE 7 120V ED100% 60HZ.
 

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