trying to understand Alk + MAG drop

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surferjoe86

Aquarium Advice Apprentice
Joined
Dec 5, 2010
Messages
23
Location
Sheffield UK
Hi

I've been dosing my tank with Mag, Alk, Cal

I'm trying to get my parameters stable at:
1380 mag
12 D/KH
450 Cal

I keep a record of all my tests.
in 5 days my parameters went from

1380 to 1200
12.6 to 8.8
465 to 465

even while dosing the correct amounts to account for coral usage ( I recorded the drop over a week of not dosing and calculated from there, broke down to a daily dose etc)

in the last 5 day's I've had a hair algae issue - I'm dosing vodka/vinegar mix to reduce nitrate/ phos (have been for 2 years with good results) also added GFO 4 days ago.
I suspect that the low Mag isn't helping the situation.

What would cause such a drop in Mag and Alk?? my doser is working correctly. I haven't done a water change in 2 weeks.

any advise would be great

cheers joe
 
Do you have a lot of sps and are you seeing good growth? If so maybe you're dosing the right amount of calcium but should increase mg and alk?
 
Hi
thanks for the quick response

I have very little coral at the moments 3 small sps colonies in a 300 liter system.
I lost a lot with the freak uk hot weather,
I have increased the Mag and Alk accordingly to account for the drop. I'm just not sure why it would drop that much in 5 days??
cheers joe
 
I could be wrong but I've personally experienced issues with dosing both mag and cal at te same time. I think I heard it oxidizes? I may be wrong but that may be worth looking into. My alk numbers were all over the place and then my lfs told me to space my dosing a few hours apart. Within days all my parameters leveled out
 
With 3 small sps colonies I would just do water changes to keep things balanced. You could let your calcium level fall a bit. Anything over 400 should be fine.
 
Agreed, you shouldn't have to be dosing mag on a regular basis..... very little mag is utilized by corals, it's presence is more to prevent the alk & calc from precipitating out of solution.

If you only have 3 small colonies of SPS in an 80g tank, you really shouldn't need to be dosing at all......... regular pwc's should be providing those with what they need.

And, from experience, you don't need to keep your calc & alk that high, either. You'd think that keeping them at max levels will provide your corals with more food, but it just creates other problems...... I use to keep my alk right at 12dKh, and I didn't get any faster growth out of my corals, but my pumps & heaters certainly built up calcification much quicker. 400-420 calc & 8-10 dKh is plenty to supply your corals with what they need.
 
thanks for all the replies, I dose everything an hour apart, I will increase that time.
I'm wanting those high levels due to what I have read about Red Sea's tests on coral growth. I'm also really struggling to see coraline growth.

Cheers joe
 
thanks for all the replies, I dose everything an hour apart, I will increase that time.
I'm wanting those high levels due to what I have read about Red Sea's tests on coral growth. I'm also really struggling to see coraline growth.

Cheers joe

Don't chase numbers you will always be adding, every tank is different, dose half in the morning the other half in the afternoon before your lights come on.
 
Don't chase numbers you will always be adding, every tank is different, dose half in the morning the other half in the afternoon before your lights come on.

+1 to not chase numbers. I used to have plenty of issues when I tried to get my alk up really high. I now leave it where it wants to stay (at about 8) and all is well. Much less of a headache too
 
It is interesting to note that most people having significant drop of mag, alk and cal are those that are using reactors. In some ways I know that skimmer has an effect on these elements. It's true that you don't need to have a high alk. as long as it does not drop down below 7. An easy way to explain the balancing act is that, once you have a good cal reading you need not adjust mag and alk. You only raise mag if it drops below the safe side and if you need to dose cal. The alk on the other hand has a reverse effect on cal. To explain why it dropped in your case is because your cal is already too high and therefore dosing will only drop your alk even more because it is already over saturated. The simple fix is pwc.
 
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