Cant stop Alk/Ca from dropping

clownsrcool · Oct 28, 2015

Just when i think i have my tank stability figured out my levels start to randomly drop and I can't seem to get it leveled out. My total volume is about 110g.

My levels currently are:
Salinity - 1.025
PH - 8.25 - 8.44
Ammonia - 0
Nitrite - 0
Nitrate - 0
Phosphate - .05
Ca - 365
Alk - 7.168
Mg - 1600

To give you an idea of what my struggles with my all have looked like here are my levels for a while back:
10/28 - 7.168
10/27 - 7.28
10/25 - 7.336
10/24 - 7.392
10/23 - 7.672
10/19 - 7.728
10/18 - 7.896
10/16 - 8.008
10/14 - 8.12
10/8 - 8.624
10/5 - 8.008 (Dosed 50ml over the following 3 days based on BRS calculator)

I dose the BRS 2 part additives.

I didn't track exactly how much i have increased my dosing amounts by but i think its close to 12ml in that time frame. Its still going down. Its not making any sense to me. I dose a total of 76ml now per day. I want to run my alk about 8.5 if i can.

I have other questions too. My Mg has been steadily creeping up on me and i can't figure out why either. I have never dosed anything for Mag because it started off at 1300 over a year ago and keeps climbing. I use normal IO salt and do water changes about every 3 weeks on avg. I don't know if it hurts for it to be that high or how to reduce it.

Thats all of the important info i can think of so ask if you need to know anything else.

Spit.fire · Oct 29, 2015

try using bulk chemical for dosing, just as good and alot cheaper

when my system had sps (crashed my tank due to a bad bucket of salt) i would loose 2 full points on alk over 20 days if i turned my calcium reactor off

Randy Holmes-Farley · Oct 29, 2015

What size aquarium are we talking about? DO you have much in the way of hard corals or coralline algae?

76 mL per day of my DIY two part (like BRS sells) is only 1 dKH per day in a 100 gallon tank. That's not much at all.

Even rapidly growing coralline in a soft coral tank can use up 2 dKH per day, and rapidly growing hard corals will often take more than 2 dKH per day.

clownsrcool · Oct 29, 2015

It's a 90g tank and close to 110g total volume. I have all SPS but most are small frags. I would say about 25 frags in all. My back glass is covered in coralline but it's not really spreading anywhere else

Randy Holmes-Farley · Oct 29, 2015

OK, so the amount you are dosing is not a problem and I'd raise the daily dose of both parts to 85 or 90 mL per day and see what that does.

Also, I'd make a one time boost to the calcium with about 500 mL of it spread over a couple of days. That will boost the calcium to about 420 ppm.

clownsrcool · Oct 29, 2015

I have also been wondering something that I don't know how to figure out. So everyone says to dose both Alk and calcium in equal parts. In doing that for a given value of alkalinity you will have a corresponding value of calcium. So for example I may wish my levels were 8.5 & 430 but at that Alk my calcium may only run at 410 or something. How do you determine that relationship between the two to figure out what one should be in relation to the other? That way I can tell things like it one param looks much lower than it should for one or the other. Also I can use that when looking at my fresh mixed salts. I can quickly see if my calcium is considered low for the Alk level I try to target and maybe being that up in my water change tank before I use it?

Randy Holmes-Farley · Oct 29, 2015

Equal parts dosing of a properly made two part, when dosed in a way to keep alkalinity stable, will keep calcium approximately stable as well (wherever it is, high, low, or just right).

That is because calcium carbonate deposition in coral skeletons and such use calcium and alkalinity in an approximately fixed ratio of 18-20 ppm of calcium for each 1 meq/L (2.8 dKH) of alkalinity. Good two part systems will roughly match this ratio.

There are a few processes that mess with this ratio of consumption in a reef tank, and most notable among those are water changes with a mix that does not exactly meet the parameters of the tank.

It is OK to add more calcium than alkalinity each day if that is what you find is needed.

clownsrcool · Oct 29, 2015

Well for a given dkh reading of alkalinity is there a way to calculate what the corresponding calcium level should be in a balanced system? I guess that is what I am after with that question.

Randy Holmes-Farley · Oct 29, 2015

clownsrcool said:
Well for a given dkh reading of alkalinity is there a way to calculate what the corresponding calcium level should be in a balanced system? I guess that is what I am after with that question.

There is only one reasonable definition of balanced (IMO), and it should not necessarily be taken to mean a desirable target level.

That definition is taking the NSW levels of calcium and alkalinity (about 7 dKH and 420 ppm calcium) and adding or subtracting calcium and alkalinity in the same ratio present in calcium carbonate. These, for example, are balanced in that sense:

5 dKH 406 ppm
6 dKH 413 ppm
7 dKH 420 ppm
8 dKH 427 ppm
9 dKH 434 ppm
10 dKH 441 ppm

etc.

The reason these are "balanced" is because one could allow corals or abiotic calcification to bring any of the higher ones back to NSW levels, and one could use any "balanced" calcium and alkalinity addition method to raise them (a CaCO3/CO2 reactors, limewater/kalklwasser, or a two part systems).

As to desirable target levels, I do not think the optimal calcium level, for example, necessarily rises just because the alkalinity rises. In fact, reefs are fairly insensitive to the calcium level as long as it is not below about 380 ppm. So 400, 420, 450, 500 ppm are all fine.

clownsrcool · Oct 29, 2015

Ok I have bumped the dosage up to 85 ml and will dose 100ml per day of calcium until I've done the 500 you suggested

Rjramos · Oct 29, 2015

The Reef Chemistry Calculator might give him the answer he is looking for. The alkalinity side gives you, "balanced calcium is;" and calcium, " balanced alk is". Don't have the link.

thedru13 · Oct 29, 2015

Here ya go
http://reef.diesyst.com/chemcalc/chemcalc.html

Randy Holmes-Farley · Oct 30, 2015

clownsrcool said:
Ok I have bumped the dosage up to 85 ml and will dose 100ml per day of calcium until I've done the 500 you suggested

That 500 mL needs to be above what is needed to offset the alkalinity additions. So it will take a long time to reach 420 ppm this way. Like a month.

Randy Holmes-Farley · Oct 30, 2015

Rjramos said:
The Reef Chemistry Calculator might give him the answer he is looking for. The alkalinity side gives you, "balanced calcium is;" and calcium, " balanced alk is". Don't have the link.

That calculator gives exactly what I discussed above. It should definitely not be used as recommended set of values.

For example, if calcium is at 500 ppm (which is OK), the "balanced" alkalinity value is almost 20 dKH (by the calculator), but alkalinity should not be kept that high.

clownsrcool · Oct 30, 2015

I understand the desired range for each parameter.

I am dosing the 500ml manually and in addition to the daily 85 ml.

So let me ask you this. What I have been doing currently which may be wrong is testing my Alk every few days and if I notice a drop I'll bump up my dosage amounts. I figure the extra addition of Alk and ca throughout the day will slowly raise it back up and hold it at a given level eventually based on how much I raised it. Is this the correct way to go about it? Should I be stepping up my dosage and manually dosing a one time amount to raise me back up?

Randy Holmes-Farley · Oct 30, 2015

clownsrcool said:
So let me ask you this. What I have been doing currently which may be wrong is testing my Alk every few days and if I notice a drop I'll bump up my dosage amounts. I figure the extra addition of Alk and ca throughout the day will slowly raise it back up and hold it at a given level eventually based on how much I raised it. Is this the correct way to go about it?

Yes, that's a reasonable approach. The only issue is that the daily demand for calcium and alkalinity depends itself on the alkalinity. So it takes more every day to maintain 11 dKH than 7 dKH. For that reason, figuring out the dose needed to maintain a certain level involves some trial and error adjustments.

clownsrcool · Oct 30, 2015

Tested again today and Alk dropped another .10 now down to 6.944. This just doesn't seem right. Nothing seems to make my Alk level off

clownsrcool · Oct 30, 2015

I've dosed about 150 of the additional suggested 500ml of calcium only so far and calcium is already up to 400.

Are you sure I shouldn't be dosing additional Alk too? I thought if one param got much higher than the other it would make the imbalance even worse and drive the lower param down even further?

Randy Holmes-Farley · Oct 31, 2015

There is probably some testing error in the calcium numbers, but if it seems to be getting close to your goal, then there's certainly no need to add all of that 500 boost.

If you dosed 500 mL of additional alkalinity along with the 500 mL of additional calcium, it would boost alkalinity by about 8 dKH, so you definitely do not want to add that much.

The 85 mL per day was a guess. You might try bumping it to 100-110 mL per day and see if that stabilizes it about where you want it. Raise both of them for this daily addition.