Should I start dosing?

Hannahmunt

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Ive been testing regularly but noticed my magnesium is always low at 1140.
I have a gag of aqua forest magnesium powder but cannot work out how to use it.

my rank is 160litres with softies and lps. I use rowa carbon and have a hang in back skimmer.

I am currently dosing nopox daily along with redsea coral food.

I use natural sea water and do a 20% change every two weeks.

if I do start to use the aqua forest magnesium, how much should I dose a day?

current parameters:
Dkh: 8.9
Calcium: 530
Nitrite: 0.1
Nitrate: 25
Phosphate: 0.25
Ph: 8.3
Ammonia: 0

the tank is two months old with one cromis and cuc
 
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Ive been testing regularly but noticed my magnesium is always low at 1140.
I have a gag of aqua forest magnesium powder but cannot work out how to use it.

my rank is 160litres with softies and lps. I use rowa carbon and have a hang in back skimmer.

I am currently dosing nopox daily along with redsea coral food.

I use natural sea water and do a 20% change every two weeks.

if I do start to use the aqua forest magnesium, how much should I dose a day?

current parameters:
Dkh: 8.9
Calcium: 530
Nitrite: 0.1
Nitrate: 25
Phosphate: 0.25
Ph: 8.3
Ammonia: 0

the tank is two months old with one cromis and cuc
Hanna, for the sake of my sanity, how did you get your alkalinity good?
 
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Hannahmunt

Hannahmunt

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When have you been testing and what test kit do you use? Is the Mg higher right after the 20% water change? What is the Mg of the seawater you are using?
I’ve been using salifert for mg and hanna for the rest. Just ordered the new hanna test for mg.

I’m doing my water change tomorrow so will re test then and test the salt water before adding it to the tank.
 

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I’ve been using salifert for mg and hanna for the rest. Just ordered the new hanna test for mg.

I’m doing my water change tomorrow so will re test then and test the salt water before adding it to the tank.
I'd test before and after the water change. That will be a good way to know how much your corals are using, and how much to dose. Low Mg is not good in general, so if the saltwater isn't within range then you also know you need to adjust it (add Mg) at every water change.
 
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I’ve been using salifert for mg and hanna for the rest. Just ordered the new hanna test for mg.

I’m doing my water change tomorrow so will re test then and test the salt water before adding it to the tank.
Hanna, you keep stating you use natural sea water. Where do you get it? May have no relevance but I’m curios.
 

Randy Holmes-Farley

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There should be no way (without dosing calcium in large amounts) for true natural seawater to get to 530 ppm calcium, which is much higher than 35 ppt seawater, and magnesium to be at 1140 ppm, which is well below 35 ppt seawater.

I expect that one or both readings are test error.

What do you think the salinity is and how was that measured?
 
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Hannahmunt

Hannahmunt

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There should be no way (without dosing calcium in large amounts) for true natural seawater to get to 530 ppm calcium, which is much higher than 35 ppt seawater, and magnesium to be at 1140 ppm, which is well below 35 ppt seawater.

I expect that one or both readings are test error.

What do you think the salinity is and how was that measured?
I used the salifert test and it read my calcium reading as 470. The hanna checker was reading 530. Maybe I didn’t do the test right.

I measure salanity using one of these: https://www.aqua-one-spare-parts.co...FjHLn2eXWE80vg1bzUwdfr6e6ZjSnqfMaAhoWEALw_wcB
 
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Hannahmunt

Hannahmunt

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According to the website these are the parameters of their water:


Salinity 34-36 ppt
Nitrates 0-0.9
Nitrite 0
Calcium 400-450ppm
Alkalinity 7.5-8.6dKH
Ammonia 0
PH 8.0-8.3
Magnesium 1250-1350ppm
Phosphate 0-0.05ppm
Silicate 0-0.1

sorry you must all be getting ticked off with my questions!
 

Randy Holmes-Farley

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According to the website these are the parameters of their water:


Salinity 34-36 ppt
Nitrates 0-0.9
Nitrite 0
Calcium 400-450ppm
Alkalinity 7.5-8.6dKH
Ammonia 0
PH 8.0-8.3
Magnesium 1250-1350ppm
Phosphate 0-0.05ppm
Silicate 0-0.1

sorry you must all be getting ticked off with my questions!

I saw that on the web site. Natural seawater at 34-36 ppt does not have alkalinity that high. I'm not sure why they think (or do) get higher values. The other things are reasonable.

I do not know how accurate that hydrometer is, but it will need a temperature correction if not at exactly the calibrated temp for it.

Was that needed and did you do it?
 
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Kmst80

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I used the salifert test and it read my calcium reading as 470. The hanna checker was reading 530. Maybe I didn’t do the test right.

I measure salanity using one of these: https://www.aqua-one-spare-parts.co...FjHLn2eXWE80vg1bzUwdfr6e6ZjSnqfMaAhoWEALw_wcB
I found my Hanna calcium checker was off by miles, gave me in th high 500s.Finally double checked with red sea test and it was actually low with 370.
Someone was saying youre supposed to use demineralized Water as top up with Hanna calcium test.
 

anthonymckay

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I found my Hanna calcium checker was off by miles, gave me in th high 500s.Finally double checked with red sea test and it was actually low with 370.
Someone was saying youre supposed to use demineralized Water as top up with Hanna calcium test.
Yep, use RODI water with the hanna calcium checker. Another mistake people make is they add 1ml reagent, and 10ml of water (11ml total) instead of the 1ml reagent + 9ml of water to have a total 10ml fluid. The directions could be a bit more clear about that.
 

Kmst80

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Yep, use RODI water with the hanna calcium checker. Another mistake people make is they add 1ml reagent, and 10ml of water (11ml total) instead of the 1ml reagent + 9ml of water to have a total 10ml fluid. The directions could be a bit more clear about that.

I used to use rodi water and the reading was way off.
I got told not to use rodi water but only demineralized water.
Either you have to be way to accurate with those tests or something is wrong with the rodi water.
I gave up on it and switched to titration and i get the same result when double checking.
 
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homer1475

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RO/DI does not work with the calcium checker. Has to be distilled(don't ask me why, I have no idea. Just what hanna told me when I emailed them). Does calcium make it past RO/DI? Something for @Randy Holmes-Farley to answer?

Also the sample size is so small, a single drop in either direction will give wildly different results. It's the one hanna meter no one suggests using.
 

Randy Holmes-Farley

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I used to use rodi water and the reading was way off.
I got told not to use rodi water but only demineralized water.
Either you have to be way to accurate with those tests or something is wrong with the rodi water.
I gave up on it and switched to titration and i get the same result when double checking.

The Hanna calcium checker is freakishly sensitive to calcium in the blank due to a poor design, IMO. Not everyone's RO/DI will be low enough in calcium.

On the technical side, RO/DI is demineralized water. Distilled water is also demineralized water.
 
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Hannahmunt

Hannahmunt

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I saw that on the web site. Natural seawater at 34-36 ppt does not have alkalinity that high. I'm not sure why they think (or do) get higher values. The other things are reasonable.

I do not know how accurate that hydrometer is, but it will need a temperature correction if not at exactly the calibrated temp for it.

Was that needed and did you do it?
Im not sure how accurate mine is, I’ve been using it since the start.

did my reading this morning and this is what they are:

Dkh: 7.9
Ca: 475
Mg: 1370

my nitrate is still reading high at 10pm but am dosing with nopox so hopefully that comes down soon.
 
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Randy Holmes-Farley

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The values are fine and I'd stop frequent testing except maybe alk once every few days to a week.

Calcium and magnesium aren't actually changing if alk is reasonably stable. Those changes are just random test differences.
 
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Hannahmunt

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I
The values are fine and I'd stop frequent testing except maybe alk once every few days to a week.

Calcium and magnesium aren't actually changing if alk is reasonably stable. Those changes are just random test differences.
I’ve been doing water changes every fortnight, so maybe I need so start doing them weekly instead?

I do around 10% every two weeks.

would you recommend I do 10% every week instead?
 

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