Adjusting the levels of your saltwater mix prior to use in the reef tank - ReefFAQs
Adjusting your saltwater mix to match your desired reef tank parameters has likely never crossed your mind. The solution for maintaining more stable water chemistry and taking your coral growth and coloration to the next level, could very well lie in this process.
For example, if you strive to maintain 450 ppm of calcium in your display tank but the salt mix you are using mixes at 410 ppm, than you are working against yourself. Each time you perform a water exchange using that salt mix, you are inching further and further from this target number. The same case applies for alkalinity and magnesium.
Is it right for you?
The decision to adjust your salt mix should be weighed carefully and in order to decide, consider three factors.
- • The type of corals you are keeping.
- • How far apart are the salt mix and your desired parameters?
- • How much and how often are you exchanging water?
The type of reef tank and corals you keep plays a big role. Many soft corals such as leathers, zoanthids, mushrooms and even most LPS are quite forgiving to subtle changes in chemistry. So instead of going through the hassle of adjusting, simply choose a salt mix that most closely matches your desired parameters.
The second determining factor would be how far is your salt mix from your desired parameters. At less than a 10% difference, the effects of a water change are null and we would not recommend you consider adjusting your salt mix. Anything over 20% would likely lead to drastic changes in the chemical composition of the saltwater further adding to your problems of stability. So if your salt mix is more than 20% off from your desired levels, just choose a different salt mix that more closely accommodates your tank.
Just to provide a reference here, based on the WWC recommended levels of 8.6 dKH alkalinity, 480 ppm calcium and 1440 ppm magnesium, a 10% difference would be about 7.7 dKH, 432 ppm calcium and 1296 ppm magnesium. These are perfectly acceptable levels for a salt mix but if you calculate a 20% difference, that puts the levels at 6.88 dKH, 384 ppm calcium and 1152 ppm magnesium which are a far cry from being acceptable and should very well be ditched for a different salt mix.
Finally, consider how often you change water. A 10% water change once per month will have minimal impact and adjusting your levels should not even be a worry. If you are changing that same 10% on a weekly basis with salt mix that is roughly 20% off your target levels, the measurable difference will be significant.
If you have sensitive corals that thrive on stability, are using salt mix that tests with parameters somewhere between 10 - 20% lower than your desired levels and perform very regular water exchanges, adjusting the levels prior to use may just be the answer to keeping more stable conditions inside your display.
Here is what happens
To further confirm why the amount of change and frequency at which you do the water exchanges are important, we can look at the impact on the total chemical make-up of your premixed saltwater.
For example, a small adjustment of 1 - 2 dKH or 20 - 40 ppm of Calcium will not likely have any effect on the overall salinity level, however, a change in Magnesium of say 200 ppm or more will likely increase salinity because of the added Magnesium salts. Once you dilute it back down to 35ppt with more fresh RO/DI water, the chemistry and elemental ratios of the entire mix is going to change.
With all of this in mind, do not make adjustments if the salt mix is so far off that you risk changing the salinity levels. This is most likely to happen with Magnesium and in the event your salt mix’s Magnesium level is more than 20% off your desired parameter, simply choose a different salt mix that is closer to your target.
Choose the right salt mix
The underlying message here is that there are so many brands of salt mix out there and many of them have proven to produce epic reef tanks and it just doesn't make a ton of sense to select one that is intentionally way off your desired calcium, alkalinity and magnesium levels. The cost difference is going to be +/- $4.00 per month in terms of the cost of salt mix for a majority of tanks and once you consider the added costs of frequent testing and chemicals needed for adjustment, it really just evens out.
The only exception to that is if your desired salt mix does something uniquely well that makes the effort of adjusting worth it. Maybe it comes in convenient single use pouches, mixes a ton faster than others, it is visibly cleaner or has some kind of definable purity standard like pharmaceutical grade components or maybe it just keeps the mixing bin cleaner and requires less work to maintain.
If any of those things are what you are after and you found a salt that does that uniquely well for you, than it may be worth the effort of tweaking the levels ever so slightly to provide a more consistent environment and here is how you would do it.
You can use any alkalinity, calcium or magnesium additive you want, but the vast majority of reefers use Sodium Bicarbonate, Calcium Chloride and the general adjustment Magnesium Mix, respectively. These options will have the most minimal impact on the overall chemistry and BONUS! ...are also the most economic options.
Using the BRS Aquarium and Reef Chemistry Calculator, first choose your desired parameter for adjustment, followed by the particular product type you are using. Enter the amount of water you are mixing, select the current measured level and then finally the desired target level. Hit calculate and it will give you the exact amount of solution you need to add into your premixed saltwater to reach your target.
Add that solution to your salt mix and test for the desired parameters.
The process is the same for all three major elements; calcium, alkalinity and magnesium. Just be sure to select the right product type and parameters. After all, the accuracy of this calculator is all based on the accuracy of your entries.
Simple as that, proceed to perform your regular scheduled water exchange and watch your reef tank thrive with stability.
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