2 part dosing... Excessive.... or just me?

[a6walter1]

I have an SPS dominated 75 gallon tank, and I'm dosing 81 mL per day right now, and I thought that was a lot. I would test for Mag, if your Mag is low it could cause the elements to precipitate out.

Furthermore, I can debunk the theory of "don't dose at the same time". I have been dosing for 2 years at the same time and not had any issues with precipitation. Just make sure you dose into an area that has adequate flow and at a slow enough rate for the elements to dissolve in the water before combining with each other.

 

[morpheas]

I'm not sure how precipitation occurs (scientifically)

Well, naturally the carbonate and calcium have the tendency to form calcium carbonate as it is. A major component that keeps them soluble in water is magnesium (hence nudges to test and test and verify it). You can learn more from the BRS 160 videos specifically this one.

On the other thand, what @a6walter1 is saying is not false. Actually, I use a medical grade infusion pump that constantly drips both solutions in the same compartment in the sump. That compartment is a high flow area which allows for the components to rapidly enter the solution rather than have the time to precipitate.

So, how sure are you about your magnesium level? Now that you are cleaning, did you notice anything out of the ordinary? Any pileup of deposit somewhere in the sump?

 

[morpheas]

As a follow up, it is not harmful to raise magnesium levels a little. What you could potentially do (especially if you have magnesium chloride laying around) is to dose enough to raise 100 ppm your level and observe your system's behavior. Is it holding more carbonate in solution? Is the dropping rate decreasing? You can use the BRS dosing calculator to determine how much to dose.

If I were in your shoes, with what you see and describe, I would strongly feel that there is precipitation occurring and the number one line of defense against it is magnesium. Seeing that you can't hurt the system with a slight increase (say 100 ppm) I would definitely do that.

If that solved the problem, I would check my testing kits, salt etc. If it didn't I'd go back to the drawing board without having really harmed anything...

 

[a6walter1]

I agree with @morpheas

I most certainly did not convey my point as well as he did.... But, Magnesium will absolutely cause precipitation issues.

I don't recall but did the OP say what kind of salt they were using?

 

[Eric83]

After cleaning Alk was 6.1dk

Did roughly 40% water change, and it's now at 8.9dkh. fingers crossed it is more stable now

 

[Eric83]

mag was tested on 2 different kits, one brand new. Range was 1380-1460.

 

[Eric83]

It's been 3hrs since water change, wanted to test again before I went to bed,

dkh is 8.8

So far so good. A lot better than the 0.9dkh drop I saw in the first 4hrs after stopping the dosers yesterday.

 

[Eric83]

At 8.6dkh. A 0.3 drop over 14hrs later.

Feeling relieved.

Quick math on required dose is about 0.35ml/gal/day to maintain Alk, which sounds a lot more reasonable than the 5.7ml/gal/day I had been dosing. I'm gonna let it slide to about 7.5dkh and do the math over a longer period of time to get a better data set before I do the calculation to determine my actual dose.

So it seems the solution was:
1. Stop Dosing
2. Tank/sump cleaning *Not sure if a through cleaning before water changed made a difference, but probably cant hurt.
3. Large water change (40% in my case)

 

[BigJim]

Great news! That was a new situation to me. You saved yourself a lot of maintenance and money.

 

[aaron23]

my apex dos is programmed to dose the alk through a 12 hour period and the calcium is dosed 10 minutes after the last alk dose so theres no interaction between the two

 

[Eric83]

24hrs = 8.2dkh down from 8.9dkh

It seems that the drop is actually speeding up:
0.3 drop in first 14hrs vs 0.4 drop in last 10hrs (.021/hr vs 0.04/hr)

Out of an abundance of caution I decided to add enough Mg to raise levels by 100ppm. Based on advice here and other forums it seems that it can only help, with little to no down side.

 

[morpheas]

24hrs = 8.2dkh down from 8.9dkh

It seems that the drop is actually speeding up:
0.3 drop in first 14hrs vs 0.4 drop in last 10hrs (.021/hr vs 0.04/hr)

Out of an abundance of caution I decided to add enough Mg to raise levels by 100ppm. Based on advice here and other forums it seems that it can only help, with little to no down side.

Agreed.

On a side note, you can't really compare the rates within the day because the calcification rates change (lights on vs off, pH change etc). The safer way is to compare within a 24 hr period and even safest is to get an average of a week or so. Of course you're gonna have to dose within a week but you can take a reading at the same time every day to establish a trend.

 

[Eric83]

True, first 14hrs would have been dark period, next 10 mostly light.

 

[shoelaceike]

when I had only LPS, I didnt dose anything and my tank was super healthy. Even now, with a mixed reef I only dose a few times a week, often just guessing. I think you can go a few days of not dosing and test and see what is actually happening

 

[Eric83]

8.1dkh.

Looks like the Mg may have helped, only 0.1 drop in last 12hrs

 

[Drauka99]

Good deal, I fought this almost exact same battle. Be sure to calibrate your dosing pumps before restarting and be sure to dose everything in balance. It sounds as if your system has found the calcium/alkalinity balance it prefers.

 

[Eric83]

8.0dkh That's just 0.2dkh drop in last 24hrs.

It looks like everything is back in order. I'll let it slide for a couple more days before hand dosing back to 8.0 or so and then base doser schedule on subsequent multi-day drop rate. So it'll be another week before I have a firm handle on what the doser schedule needs to be.

I think that's it for this thread, thanks for all the input and help!