Alk swing and dosing

[brianisoutside]

So I’ve started noticing my alk dropping pretty quickly. But my calcium is basically unchanged?

I typically changed 5 or 10 gallons of water every week, tank is a 57g with 20g sump

I’m using salifert test kits, here is the last few days. What do you think? Time to start dosing 2 part?

 

 

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[WheresTheReef]

It might be a good idea to dose to bring the alk level up a little. However, can you tell us more about your tank? How long has it been running? Livestock? Can you share a pic of your tank? For about the first year of my tank alk dropped way more than calcium since the tank wasn’t fully cycled. Now I dose a little more calcium than soda ash, but the dosages are very close. 

[brianisoutside]

It has been setup for a year.

Blue damsel, Wyoming clown, tailspot blenny, clown goby, sharknose goby, royal gramma and a six line wrasse.

 

[epleeds]

You def want to get a handle on the ALK swings especially if you want to go the SPS route. My ALK/CAL levels when I was dosing we’re always different. I never dosed the same amount of each solution. 
 

I would probably pick up a BRS doser to dose ALK to keep it steady. I like keeping mine around 8.0-8.2

[davelin315]

Check Magnesium, too.  Calcium and Alkalinity are kind of like a see saw, they bond with each other and form insoluble Calcium Carbonate (or is it bicarbonate?).  If your alk is going down quickly could just be that it is bonding with the calcium which is in higher concentrations.  Magnesium occupies these bonds but allows it to be used still.  Does not look like you have a lot of corals in the tank so check that before starting to dose.

[brianisoutside]

2 hours ago, davelin315 said:

Check Magnesium, too.  Calcium and Alkalinity are kind of like a see saw, they bond with each other and form insoluble Calcium Carbonate (or is it bicarbonate?).  If your alk is going down quickly could just be that it is bonding with the calcium which is in higher concentrations.  Magnesium occupies these bonds but allows it to be used still.  Does not look like you have a lot of corals in the tank so check that before starting to dose.

I will double check mag when I test tonight

Edited February 10, 2020 by brianisoutside
Post

[WheresTheReef]

I agree nothing in your tank to really deplete your alk. Mg is a good point to check, but looks like it's sitting around 1350 based on your notes above. Randy explains why Alk can drop during the cycling process in link below. 

 

https://www.reef2reef.com/threads/alk-and-calcium-dropping-with-no-corals.293654/post-3584815

 

[madweazl]

Check it again this evening and see where it is at. Much lower and consumption is going to slow down a bit and make it a little tougher to see where you're at but there is nothing wrong with the current level of 6.8 dKh (about was natural sea water is actually). Based on the three days of results, .6 dKh looks to be the average (another test will narrow this down) and is feasible just with coralline growth. Don't confuse the dropping rate (consumption) with an alkalinity swing; nothing that is happening right now is negatively impacting your corals. 8 dKh one day and 6 dKh the next and back to 8 dKh is what you're trying to avoid.

[brianisoutside]

5 hours ago, madweazl said:

Check it again this evening and see where it is at. Much lower and consumption is going to slow down a bit and make it a little tougher to see where you're at but there is nothing wrong with the current level of 6.8 dKh (about was natural sea water is actually). Based on the three days of results, .6 dKh looks to be the average (another test will narrow this down) and is feasible just with coralline growth. Don't confuse the dropping rate (consumption) with an alkalinity swing; nothing that is happening right now is negatively impacting your corals. 8 dKh one day and 6 dKh the next and back to 8 dKh is what you're trying to avoid.

Sounds good. I changed 5 gallons of water last night as part of my routine. I’m curious to see what it’s at now and over the next couple days. I think over the next month or so I may pick up some kind of doser / controller anyway.

[madweazl]

The water change is going to throw off your numbers so it wont be possible to accurately say what your daily consumption is for now but monitor it (the alkalinity) over the next few days and note it. What salt are you using? They all mix up to differing levels; if you really like a particular salt mix (for whatever reason), it's easiest to keep your alkalinity at whatever it mixes up as. I prefer Instant Ocean which mixes up around 10.7 dKh (for me) but I like to run my tank around 7 dKh so I had to manually lower the levels before use. If it were +/- 1 dKh of my desired levels, I'd just leave it be and run with it; if you're doing water changes in the 10-15% range it wont have much of an impact on your overall alkalinity so it isnt worth messing with at that point. 

[Origami]

On 2/5,you listed "Na25" just before your phosphate measurement - what did you mean?

[brianisoutside]

On 2/5,you listed "Na25" just before your phosphate measurement - what did you mean?

Nitrate of 25

I realize the water change would move the numbers a bit. Part of me wanted to see just how much. That’s also why I tested the new water, just to see where that was at too. I am using the orange reef crystals salt.
So tonight was Mg 1315, Kh 7, Ca 455
Thoughts?


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[Origami]

Well, the good news is this: Your calcium and alkalinity are declining at reasonable rates. How do I conclude this? Well, according to your notes, your calcium declined 15 ppm between 2/6 and 2/9. Now, I never recommend that you try to conclude anything from hobbyist-grade test kit results over really short spans of time. However, when we look at how much your alkalinity decreased in your first post (1.6 dKH), we see that calcium declined ~15 ppm during the same time.

 

Under normal circumstances, when a tank is fully cycled and stable, and all nitrate is being converted to nitrogen gas to complete the nitrogen cycle, calcium is consumed at a nominal rate of 20 ppm for every 2.8 dKH of alkalinity. There are minor variations to this ratio based on your tank occupants (as much as 5% less in some tanks) but that's a fundamental rule-of-thumb value. In your case, the 1.6 dKH drop in alkalinity corresponds to an ~11.5  ppm change in calcium. Given that we all use hobbyist-grade calcium test kits, the measured 15 ppm decrease in calcium is quite reasonable. 

 

The reason I asked about the "Na" annotation is as follows: As long as your tank is generating nitrate and you're managing nitrate (i.e. exporting nitrate) through water changes, your alkalinity will decrease at a faster rate than normal calcification would suggest. 

 

This previously-cited ratio (20 ppm of calcium for every 2.8 dKH of alkalinity) assumes a fully cycled tank. However, in a tank with incomplete nitrification, where nitrate is accumulating and is exported/managed via water changes, the ratio can be significantly less. The reason for this is that the nitrogen cycle itself consumes one unit of alkalinity in going from ammonia to nitrite to nitrate, and it returns one unit of alkalinity in going from nitrate to nitrogen gas. The entire process is alkalinity-neutral but, if you export nitrate through water changes, you'll basically take an alkalinity hit for it above and beyond what is consumed in calcification.

 

 

 

 

[Origami]

BTW, how long have you had this tank set up? I'm assuming also that you're fairly new to the hobby. Is that correct?

 

I see that you're testing daily. We tend to do that when we're just starting out. I know that I did - daily at least; sometimes more. It's part of our learning experience. As you get more familiar with your tank, you'll test far less and you'll be more selective with what you're testing. You'll also learn to look at your tank and recognize when things are going well and when they're not. One thing to realize is that our hobbyist-grade test kits have limited resolution and repeatability. That knowledge should temper our impulse to conclude or to act based upon measurement data taken over too short a baseline. It's like trying to drive a car by looking out only five feet in front of you: There will be a tendency to over-correct and drive into instability. That's why I looked at your three-day record and ignored the day-to-day changes in data. 

 

Now, as you get more comfortable with testing less, you may find that you're testing alkalinity once a week and calcium once every two weeks, or even less. Because you're looking into your tank and recognizing the signs of a healthy, happy tank, you'll test only to confirm what you already see. During this time, you're using testing as a means to monitor your tank. However, when things start to look different, you'll start to test for diagnostic reasons. The objective of diagnostic testing is different than monitoring testing. It's intent is to diagnose and provide information that is used to shape your response/action to observed changes in your tank.

 

One other lesson to learn early on is that test kits are not infallible. If you get results that are not borne out by your other observations, of seem out of whack, then don't be quick to trust the data. More than one tank has been led down a dark path from a bad test kit, whether expired or part of a bad batch from a manufacturer. Check, double-check, and cross-check before making any unexpected, drastic change to your tank.

[brianisoutside]

The tank is about a year old. I never really tested much after cycling. I just trusted the water changes. Even when I did test I was more worried about nitrate and phosphate. Alkalinity, calcium and others were an after thought as I never really understood them.

I’ve been having problems with zoas which is what led me to start testing and trying to diagnose or find the problem. I’m not really sure anything really parameter wise is causing their issues though.



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[Origami]

Gotcha. What's up with the zoas? If you post pics and describe what you're seeing in another thread, then maybe one of our many people that run zoa tanks can offer insight into what may be going on. Include your parameters in the new post, of course. Some might say that your nitrate and phosphate levels are high, but there have been some very successful tanks that run on a combination of high nitrates and phosphates - it may be the ratio that's more important there than the actual value (below certain values, that is). 

 

Anyway, your alkalinity decline may, in part, be due to your water changes exporting nitrate which, at that point in the nitrogen cycle, represents a net alkalinity loss. Calcification (corals, shelled organisms, coralline algae, abiotic precipitation, etc.) may be where other alkalinity (and calcium/magnesium) is consumed. Overall, your alkalinity trend looks reasonable given the short baseline of data that we have.