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my system has real difficulties keeping Mg, Ca and KH stability. Kh can fall particularly quickly, a few degrees in a few days. What are the underlying issues maintaining these chemicals? Mg is relatively stable at around 1150.
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Unstable
#2
chriss 
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Posted 27 August 2009 - 09:30 PM
What are your low/high kh readings? What are you buffering with?
Regarding mag and ca, first, you need to get your mag up to around 1320 - 1350 and stable'ish, that seems quite key. Once thats up, then measure your ca and adjust accordingly. Until then just buffer the kh to keep it at or above 8. New sand can suck up mag and ca very quickly, remind us how old/large your setup is and what sort of stock you have, fish and sps in particular.
Things that can affect kh are nutrient loads, stocking density and anything depressing the ph eg high co2 levels, biological activity etc
Chris
Regarding mag and ca, first, you need to get your mag up to around 1320 - 1350 and stable'ish, that seems quite key. Once thats up, then measure your ca and adjust accordingly. Until then just buffer the kh to keep it at or above 8. New sand can suck up mag and ca very quickly, remind us how old/large your setup is and what sort of stock you have, fish and sps in particular.
Things that can affect kh are nutrient loads, stocking density and anything depressing the ph eg high co2 levels, biological activity etc
Chris
#3 Guest_jacksok_*
Posted 27 August 2009 - 11:41 PM
It's natural for alkalinity / dKH / carbonate hardness to appear to fall more rapidly than calcium. While corals tend to take up equal amount of calcium and carbonates so as to form calcium carbonate, the pools of calcium and carbonate ions in your water are of a very different size. For example: if calcium were 100 and carbonates were 20 then a reduction of 1 unit in each would represent a decrease in calcium of just 1% and a drop in alkalinity of 5%.
So depending on what your values actually are, you might not need to target alkalinity with a buffer specifically. It could be that a balanced additive that adds both calcium and carbonate in equal measures - like kalkwasser, or cranking up your calcium reactor if you have one - is all that you need to get back on track, as any addition will have a bigger % impact on dKh than calcium. But sort out that magnesium first!
HTH
Keith
So depending on what your values actually are, you might not need to target alkalinity with a buffer specifically. It could be that a balanced additive that adds both calcium and carbonate in equal measures - like kalkwasser, or cranking up your calcium reactor if you have one - is all that you need to get back on track, as any addition will have a bigger % impact on dKh than calcium. But sort out that magnesium first!
HTH
Keith
#4
Blacktip
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Posted 28 August 2009 - 09:18 AM
Thanks guys.
My KH is currently at 6.7 down from 9 last wednesday. I run a calcium reactor but boost it with bicarbonate of soda. My system is about 3 years old and is lightly stocked by reef standards. It contains about 10 sps frags and a few lps. 6 small fish and one regal tang. PH remains stable at about 8.4 lights on. Nitrates are at five ppm. Lots of O2 by surface agitation, weir, various over flows and Deltec APF600 skimmer.
Will correct Mg over the next few days and take it from there. Is there any harm incorrecting Mg and Kh at the same time?
Cheers
My KH is currently at 6.7 down from 9 last wednesday. I run a calcium reactor but boost it with bicarbonate of soda. My system is about 3 years old and is lightly stocked by reef standards. It contains about 10 sps frags and a few lps. 6 small fish and one regal tang. PH remains stable at about 8.4 lights on. Nitrates are at five ppm. Lots of O2 by surface agitation, weir, various over flows and Deltec APF600 skimmer.
Will correct Mg over the next few days and take it from there. Is there any harm incorrecting Mg and Kh at the same time?
Cheers
#5 Guest_jacksok_*
Posted 28 August 2009 - 09:48 AM
You don't say what your calcium levels are at, but I think you are in danger of your parameters yo-yo'ing around if you start targeting dKH on its own. Increase mag by around 50ppm per day and crank-up your reactor output as it doesn't appear to be keeping pace with demand. I wouldn't dose bicarb on its own unless you know that calc and alk are actually out of balance. There is an excellent calculator that can help you fine tune adjustments to the reactor here.
Keith
Keith
#6
Blacktip
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Posted 03 September 2009 - 07:42 AM
Ok, so now I have the Mg where it needs to be. Also got the kh/ca balance but too low. I'm using the calculator to get the reactor working properly. My KH of the effluent appears to be about 74KH, does that sound right?? sounds v high. Also are all reactors so difficult to run stable as mine needs constant playing with (tmc)?
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#7
chriss
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Posted 03 September 2009 - 08:06 AM
I can't really comment on the TMC unit, but with the Korallin, I find that once you've grasped the idea of how they "work" then they don't need much tweaking at all.
An effluent of 74dkh is pretty high, but not a problem unless it is driving up your tanks dkh. I guess the first step is to ensure that the effluent output is stable day to day, what value isn't really that important for now, but somewhere over 30-40 would be good. You then need to monitor your tanks dkh to see if it is rising or falling and adjust the reactor accordingly so that after a few days/week of fiddling it keeps your tank at a stable dkh.
Your adjustment options involve either adjusting the effluent drip rate or dkh.
Depending on your reactor, adjusting the drip rate which affects the contact time in the reactor can also affect the effluent dkh at the same time, but probably only if you are near the limits of your reactors abilities. Adjusting the ph controllers set point will have a direct impact on the dkh, BUT, your media will have a useable ph range and if you need to go to the extreme ends then it will stop working. These problems only really occur if your reactor is undersized or oversized and I would not expect you to encounter these issues in your setup, but it's useful to know.
Finally, don't forget to check your tanks ph. I high drip rate of low ph effluent can suppress the tanks ph, it may not be significant but can be improved by using one of Lindsay's patented bubble machines.
Hope tht helps
Chris
An effluent of 74dkh is pretty high, but not a problem unless it is driving up your tanks dkh. I guess the first step is to ensure that the effluent output is stable day to day, what value isn't really that important for now, but somewhere over 30-40 would be good. You then need to monitor your tanks dkh to see if it is rising or falling and adjust the reactor accordingly so that after a few days/week of fiddling it keeps your tank at a stable dkh.
Your adjustment options involve either adjusting the effluent drip rate or dkh.
Depending on your reactor, adjusting the drip rate which affects the contact time in the reactor can also affect the effluent dkh at the same time, but probably only if you are near the limits of your reactors abilities. Adjusting the ph controllers set point will have a direct impact on the dkh, BUT, your media will have a useable ph range and if you need to go to the extreme ends then it will stop working. These problems only really occur if your reactor is undersized or oversized and I would not expect you to encounter these issues in your setup, but it's useful to know.
Finally, don't forget to check your tanks ph. I high drip rate of low ph effluent can suppress the tanks ph, it may not be significant but can be improved by using one of Lindsay's patented bubble machines.
Hope tht helps
Chris
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