Will my calcium and Alkalinity stabilize if my water change brings them down?

Miami Reef

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Hello. I have a 300 gallon tank with new soft and lps corals. I get natural sea water delivered for my water changes once a month. I noticed that alkalinity is about 6-7 and calcium was 370-420 from the NSW.

I plan to have my system on a 2 part dosing system that will maintain my tank at 8-12 dkh and my calcium at 450.

When I do the water changes once a month, will my dosing system bring the levels back into that range? Or do I need to do a big dose at the time of the water change? There’s no way to know the levels of the ocean water until it’s in the tank.

I think this is how dosing works: Once I dial the system levels at 8dkh, that means that the corals are consuming enough alkalinity to prevent it from going higher than 8dkh But if the levels are all of a sudden at 6dkh does that mean the levels will eventually climb back to 8dkh?

I can’t explain it, but I’m new to this chemistry.
 
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Dkeller_nc

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There are reasons to use artificial salt water beyond maintaining control over major and minor elements. Probably the biggest reason is prevention of introducing unwanted pests into the tank and (possibly) adding polluted water to the tank that could harm corals. Perhaps one of the most likely introduction of pollutants is sunscreen in parts per trillion quantities. The active ingredient in modern sunscreens has been shown to be unbelievably toxic to stony corals - in the parts per trillion range.

However, and to answer your specific question, it depends on how much water you change. If the answer is a complete, 100% change, then I would certainly recommend testing and adjusting your change water to your liking to prevent shocking the animals in your reef. If it's 10%, I wouldn't bother. Most corals will tolerate a 1 dkH change in alkalinity without too much problem.
 
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blasterman

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You need to bring the NSW up to the levels in your tank. Otherwise your dosing is always in the hole.

What happens is alk drops lower and slows down calcification, so there is psuedo self correcting level, but it involes lower alk levels.
 

mdb_talon

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You have it generally correct in that if you dial in your doser to maintain 8 dkh then it will generally stay around that, but will point out there is no magic here. If coral growth slows and you dont change dosing then alk will creep up. Could go up a lot over time. Same on the other side if coral growth increases.

As for water changes if you keep your dkh at 8 and do a 50% WC with 6 then it will make it 7(25% change makes it 7.5). So assuming you are doing moderately sized changes that is not a huge swing and you can make up with it via some manual doses over the next couple days. On the other hand if you keep your dkh at 12 and use 6dkh for a 50% change then now you have dropped it to 9 which is a big sudden change(and possibly large immediate PH change also).

In any case personally i would get an rodi and make your own water. You need it for topoff anyway. Artificial water gives you much better control over parameters and control over what else is going in your tank.
 
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Miami Reef

Miami Reef

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You have it generally correct in that if you dial in your doser to maintain 8 dkh then it will generally stay around that, but will point out there is no magic here. If coral growth slows and you dont change dosing then alk will creep up. Could go up a lot over time. Same on the other side if coral growth increases.

As for water changes if you keep your dkh at 8 and do a 50% WC with 6 then it will make it 7(25% change makes it 7.5). So assuming you are doing moderately sized changes that is not a huge swing and you can make up with it via some manual doses over the next couple days. On the other hand if you keep your dkh at 12 and use 6dkh for a 50% change then now you have dropped it to 9 which is a big sudden change(and possibly large immediate PH change also).

In any case personally i would get an rodi and make your own water. You need it for topoff anyway. Artificial water gives you much better control over parameters and control over what else is going in your tank.
I do have an RODI unit. I will make my own saltwater changes.
 
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