Low dKH

Luvthekeys

Luvthekeys

Member
I have been having a problem keeping my carbonate hardness and PH at acceptable levels. Today it fell as low as 6 dKH, yesterday it was 7 and the day before 8. I have been adding Kent Pro Buffer DKH following instructions. My calcium is over 400 and Magnesium over 1500 which from my understanding help keep the dKH and Ph up. I can get it back up to 8 dKH by buffering but in a day or less it has fallen to 7 or lower. I should say everything looks fine, both coral and fish but I would like to stabilize my dKH around 9 and PH around 8,2. I am at a loss as to what would lower dKH and not affect calcium and Magnesium. Am I mistaken in my assumptions? Any ideas what is causing my dKH to fall so quickly.
 
pegasus

pegasus

Well-Known Member
Magnesium is a buffer that keeps the alkalinity and calcium ions from bonding. If they bond together, it forms calcium carbonate that is no longer available to corals (precipitates out of the solution). Normally, calcium and alkalinity levels will both fall at equal rates, so your situation is a bit different, especially since your mag level is so high. Mag should be in the range of 1250-1350ppm. If you're dosing mag, stop until it drops within this range.

I had a problem getting my alk up awhile back. I had to dose alk nearly 3x as much as cal. It took a few weeks, but once the system stabilized, I was able to dose alk and cal at the same rate. Just keep dosing alk until it reaches the target level. You also want your cal level to be around 425-450ppm (NSW is 410ppm). Don't try to get it higher than this, as high calcium levels drive down alk levels... and vice versa. There has to be a balance of these elements before you will reach equilibrium.
 
Luvthekeys

Luvthekeys

Member
jay0705 said:
Have u tested the alk of your source water?
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Good Suggestion! Just did it and it tested somewhere between 1 and 2 dKH. Could that be the reason if so why would it fall between water changes If I am buffering to try to keep it up? Does that mean I should dose my water changes when I do them. wouldnt the salt mix bring it up? I am using Reef Salts.
 
jay0705

jay0705

Well-Known Member
If the source is ok. I would guess its something w the salt. I'am not familiar w reef salts is that who makes it?
 
Luvthekeys

Luvthekeys

Member
Pegasus,

So you think my high magnesium levels are contributing to my low dKH. It makes sense since I was dosing Magnesium to get rid of some unwanted algae. I will allow my magnesium levels to drop and see what happens. Thanks to you and Jay for responding so quickly.
 
jay0705

jay0705

Well-Known Member
Ah ok. That could be the issue. I have heard people say that they have had issues w it. If u compare its make up to say red sea salt the instant is lower
 
Luvthekeys

Luvthekeys

Member
Instant Ocean and Instant Ocean Reef Salts have different compositions. I changed to from Instant Ocean to Instant Ocean Reef Salts due to low levels of calcium and Magnesium in Instant Ocean.
 
Luvthekeys

Luvthekeys

Member
Yes. I was having a problem maintaining calcium and Magnesium levels which ended when I switched to Reef Crystals instead of regular Instant Ocean.
 
pegasus

pegasus

Well-Known Member
Luvthekeys said:
Pegasus,

So you think my high magnesium levels are contributing to my low dKH. It makes sense since I was dosing Magnesium to get rid of some unwanted algae. I will allow my magnesium levels to drop and see what happens. Thanks to you and Jay for responding so quickly.
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It could be a contributing factor. It's easier to maintain levels if all elements are within specified ranges. Magnesium will only work against Briopsis, and only Kent Tech-M has been proven to work, and only when kept above 1500ppm for a week or two. I ran mine up to 2000ppm before I realized I didn't have Briopsis. It obviously has no effect on hair algae... doh! Your mag level will naturally fall, but it can take awhile to happen, as it isn't used in the same proportion as alk and cal. You can speed up the process with a couple of water changes. I also use IO/RC, and every batch I've tested has fallen within advertised ranges. If you don't have a lot of corals, simple water changes will provide all your corals need. I have a good many corals that use these elements, so I dose 100mL (each) of alk and cal daily, with a splash of mag after using up a gallon of each. I suppose if I did a water change more often, I might be able to cut back on dosage. It's only been about three months since the last water change... :eek:
 
Luvthekeys

Luvthekeys

Member
You are right I was dosing to try to rid myself of some Bryopsis and I was using Kent Tech-M. I do a fifteen percent water change weekly. However the low dKH was driving me nuts. As I said I will stop the Magnesium dosing until I get back to normal levels. Hopefully that is the problem, Until then I will keep using Kent Pro Buffer dKH.
 
pegasus

pegasus

Well-Known Member
Natural seawater has a KH of 7-8, and as long as you're above 7, you'll be okay. If it falls below 7, coral growth will begin to slow and eventually stop. It doesn't spell immediate death to your corals, so it's nothing to freak out about. Having a high level doesn't mean your corals will grow any faster, either. Corals will use only what they need for normal growth patterns, and the only advantage to having a high level is that it takes longer to reach a low, unusable level. Between 7-9 dKH is good for normal tanks. For full-blown reef tanks, 9-11 dKH is more desirable.

I didn't ask earlier, but what is your pH when alk is 7... and 8?
 
Luvthekeys

Luvthekeys

Member
My ph normally runs between 7.8 and 8.0. Only once or twice has it deviated from those two numbers in the last two and half months. I always take my PH in the morning so I guess that would be the low side. I live in Florida and this time of year the house stays a constant 74 with little or no fresh air due to the air conditioning. I am sure that has an effect on it too. Even today when my dKH read 6 the PH was 7.8 or 8.0. With the API test it can be hard to tell the difference in color.
 
bang guy

bang guy

Moderator
Just so I understand - You Alkalinity drops from 7-8dKH down to 6dKH with no associated drop in Calcium.

Is that right?
 
Luvthekeys

Luvthekeys

Member
Bang Guy,

I am using purified water from the local supermarket since I do not have RO system. the label says "ozonated deionized serves the purposes of distilled water"

I can give you my results from Sunday right after I did a water change.
PH 8.0
Cal 440
dKH 6
Mag 1480

I have been dosing Kent Pro Buffer dKH each day since then with little to no change in dKH. At least according to the API test kit I am using. It is within its expiration date. There are no nearby pet stores to confirm my readings. I am going through treatment for cancer so it hard to drive any distance. I will order a different test kit for dKH if you recommend one.

Yesterday I tested the dKH and it was 5. I did not test calcium or magnesium at that time.

Just now tested again results fo follow

PH 8.0
Cal 420
dKH 6
Mag. 1350

The 28 gal. tank is two and half months old and only has a lawnmower blenny and a royal gamma. It does have a fairly large clean up crew 3 peppermint shrimp about 20 small hermit crabs, two cleaner clams and about six turbo snails. Also one bubble tip anemone, featherduster and several corals. All look healthy.

nitrates stay about 5 ppm rarely going higher or lower.

Temp ranges between 79 and 81.

I recently had an outbreak of diatoms and red cyanobacteria which I am trying to control.

Beyond that everything looks good. I have a good growth of red macro algae and some green Macro algae. A few tuffs of hair algae which I remove when I see them.

Hope that gives you a basic idea of the tank.
 
bang guy

bang guy

Moderator
Yeah. What would really help is a chart of Calcium and ALK levels tested once a day at the same time of day for a week and any dosing listed on the chart.
 
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