Two-part dosing and Salinity?

[plankton]

Been dosing Bionic two-part for a few months now and noticed that salinity keeps creeping up on me. It's small 25G Lagoon with 10G sump. I keep alt at 8.5 dKh; temp 78 deg F, Salinity at 1.026 but will slowly creep up if I don't take 500ml of water out of tank and let auto top-off bring me back down. top-off water is RO/DI. I'm using Bionic two part. Any ideas?

 

[Larry L]

That's basically how two-part dosing works. To oversimplify, you generally dose calcium chloride and sodium carbonate, which gives you the calcium ions and the carbonate (i.e. alk) that your corals need, and what's left is sodium and chloride, i.e. NaCl = salt.

 

[plankton]

Got it. Thanks. So, watch alk/salinity carefully weekly to make sure said are stable.

 

[Randy Holmes-Farley]

I discuss it here:

The Many Methods for Supplementing Calcium and Alkalinity - REEFEDITION

Two-part Balanced Additive Systems

There are now a plethora of two-part balanced systems for supplementing calcium and alkalinity, as well as DIY recipes that I have published and for which suppliers sell quality DIY ingredients. These are always liquid additives that you add equally to tanks to supplement both calcium and alkalinity. In the DIY version, magnesium is added to the aquarium as a third solution, although it need not be added especially frequently. The rational for this type of product is that the bicarbonate and carbonate that one might like to dose to supplement alkalinity are not readily compatible with the calcium that is also needed. So one portion contains calcium and the other contains the alkalinity. When a DIY is used, the magnesium sulfate in it is not compatible with either part, so it needs its own solution.

In the simplest form, such a system would be provided by any calcium salt at one concentration in one bottle, and a carbonate alkalinity supplement in the other bottle. Within that constraint, manufacturers have a fair amount of room to play. Typically these additives claim go a step further. When the calcium and alkalinity are taken out of the picture, as they will be by calcification in the tank, then the ions that remain are often described as having the same ratios of ions as natural seawater. Assuming that this is true, then the “residue” is simply more salt for the aquarium. Over long periods of time the salinity will build up due to this process (an effect that is quantified below), but there will be no significant buildup of specific ions in the tank.

In order to accomplish this, manufacturers could use a variety of calcium salts in the calcium portion, for example. They could use calcium chloride, calcium sulfate, calcium bromide, and a variety of other similar salts. They could also put magnesium and strontium in this portion as they would not be compatible with the alkalinity component.

The alkalinity portion of these systems is more complicated. As has been shown in other parts of this article, alkalinity can be provided as bicarbonate, carbonate, or hydroxide. I don’t know of any commercial supplements that use hydroxide for a two part system, but the commercial ones do use bicarbonate, carbonate, and mixtures thereof. Consequently the pH varies substantially between brands, and the various brands of these products should not be thought of as identical for this reason, if no other. In order to attain the natural seawater residue, the alkalinity portion could contain sodium bicarbonate or carbonate, potassium bicarbonate or carbonate, lithium bicarbonate or carbonate, etc.

I’ve not seen any independent test of whether these actually produce a residue equivalent to natural seawater, but I’ve seen no particular reason to doubt it, at least for the major ions. When it comes to the trace elements that might concern some reef keepers, it seems unlikely that these products will be any less prone to having uncontrolled levels of trace compounds like copper than are commercial salt mixes, or any other supplement of calcium and alkalinity, but that remains to be determined (at least as far as I know).

One issue that has confused some reef keepers, however, is the presence of trace elements. Assuming that these products are actually formulated with every ion such that a true natural seawater residue remained (let’s call this the “ideal” product), then it will necessarily contain such ions as copper. Since copper is elevated in some reef tanks, and is toxic to many invertebrates, reef keepers have wrongly criticized this method as adding more copper. That’s actually not what would happen. Since these products leave a natural seawater residue, and since copper may be elevated in concentration in many reef tanks relative to seawater, then using these “ideal” products will actually LOWER copper levels because when the increase in salinity is corrected, the copper will drop.

For example:

You have copper in your aquarium at 4 ppb and salinity of S=35.

You add a two part additive that over the course of a month raises salinity to S=36, and raises copper to 4.02 ppb.

Then you correct the salinity back to S=35 by diluting everything in the tank with fresh water, and you get a final copper concentration of 3.9 ppb.

Does this happen in real products and not “ideal” products? I have no idea. But the statement by manufacturers that it contains all ions in natural ratios, including copper, should not be viewed as a concern that it is exacerbating a heavy metal problem.

The rise in salinity of these products over time can be very roughly calculated, though there are several reasons why this calculation is only an estimate. For every 1000 meq of alkalinity added in this fashion (and the matching amount of calcium) these products will deliver on the order of 60 grams of other ions to the tank. In a tank with a low calcification demand (defined later to be 18.3 thousand meq of alkalinity per year in a 100 gallon tank (0.4 dKH/day)) this effect will raise the salinity by 3 ppt per year (compared to a normal salinity of S ~35). In a high demand tank (defined later to be 219 thousand meq of alkalinity per year in a 100 gallon tank (4.4 dKH/day)), the salinity will rise by 35 ppt in a year, or approximately doubling the salinity. Consequently, the salinity should be monitored closely in using these types of additives, especially in a tank with high calcification rates.

Many people have begun to use dosing pumps to deliver these sorts of additives more uniformly across a day/night period with less work by the aquarist. Such pumps can be obtained starting under $100 for each part dosed this way. There is no need to dose the magnesium part this way, since very little is actually required and once a week is plenty often enough.

 

[DeputyDog95]

It's been interesting reading this thread and Randy's comments.

I dose the Red Sea liquid alk solution at 41ml a day in a 120g tank. It's a newish SPS tank (around 18 months) and I've gone from 15ml a day to the current dosing regimen of 41ml a day as the SPS and coralline have started to grow out.

Now I'm seeing a half point jump in salinity (35 to 35.5 PPT) every week or two, and am having to drain a gallon or so of tank water to let the auto top off dilute it back down to 35.5 PPT.

I may start making lower slightly lower salinity water change batches to see if that helps minimize the fluctuation.

On a side note, about 6 months ago I tried a different manufacturer's alk buffer which uses potassium chloride instead, which is supposed to prevent this salinity buffering you get with sodium chloride alk solutions. What they failed to mention was that it would drive my K through the roof and I didn't figure it out until the K got over 600. At which point I started investigating, went back to Red Sea, and then started doing 2-3 water changes a week until I got it back down to 400ish. Fortunately, nothing got smoked. But a lot of it did get very angry. I think the only reason I got away with it was that it was a slow gradual increase over a couple of months.

I guess when you are adding solutions to a system, there are always going to be things added as well you don't necessarily want...

 

[Randy Holmes-Farley]

On a side note, about 6 months ago I tried a different manufacturer's alk buffer which uses potassium chloride instead, which is supposed to prevent this salinity buffering you get with sodium chloride alk solutions. What they failed to mention was that it would drive my K through the roof and I didn't figure it out until the K got over 600. At which point I started investigating, went back to Red Sea, and then started doing 2-3 water changes a week until I got it back down to 400ish. Fortunately, nothing got smoked. But a lot of it did get very angry. I think the only reason I got away with it was that it was a slow gradual increase over a couple of months.

Which manufacturer?

Potassium chloride is not an alk supplement, and potassium carbonate would be a terrible alk supplement, as you found, as it would drive potassium through the roof on many aquaria. It will also raise saliniyy faster than sodium carbonate.

 

[DeputyDog95]

Which manufacturer?

Potassium chloride is not an alk supplement, and potassium carbonate would be a terrible alk supplement, as you found, as it would drive potassium through the roof on many aquaria. It will also raise saliniyy faster than sodium carbonate.

Maybe it was potassium carbonate then. Chemistry is not my strong suit Reef Blueprint. The guy who started Brightwell has launched a whole new line of products.

Coral8 Yin and Yang | Captiv8 Aquaculture | Reef Blueprint

Captiv8 Aquaculture. U.S.A.-based and -produced, privately-owned by scientists.

www.captiv8aquaculture.com

 

[Justdrew]

Oh Boy! Here we go.

 

[Randy Holmes-Farley]

Maybe it was potassium carbonate then. Chemistry is not my strong suit Reef Blueprint. The guy who started Brightwell has launched a whole new line of products.

Coral8 Yin and Yang | Captiv8 Aquaculture | Reef Blueprint

Captiv8 Aquaculture. U.S.A.-based and -produced, privately-owned by scientists.

www.captiv8aquaculture.com

Chris Brightwell? I hope he has learned some chemistry since his many debacles at Brightwell. Not many companies make it so easy to spot their lack of understanding of their own products , but Brightwell’s own descriptions prove it.

 

[Randy Holmes-Farley]

Oh Boy! Here we go.

lol

 

[DeputyDog95]

Chris Brightwell? I hope he has learned some chemistry since his many debacles at Brightwell. Not many companies make it so easy to spot their lack of understanding of their own products , but Brightwell’s own descriptions prove it.

Different Chris, for privacy reasons I probably shouldn't say his last name. I think he started Brightwell with Chris Brightwell and sold his portion. Or something like that... Super nice guy and seems very bright. At least to me. Again, I'm not not a chemist by any stretch and rely on people like yourselves with vastly more knowledge for my information.

His new Reef Blueprint line is actually pretty interesting. The salt was amazing. My ORP went over 400 by simply switching to his salt. It was 330 using the Red Sea blue bucket before and went back to 330 after I returned to the blue bucket. He's super particular about using very high end ingredients in the product line. It was a bit of a hassle to mix though as you had to add the salt really slowly as there was a heat reaction when it hit the water.

That being said, the products could sometimes be hard to get (startup company) and after my potassium debacle with the alk solution, I went back to using Red Sea products. When I discussed it with Chris, he said he uses his alkalinity in conjunction with kalk, so he uses significantly less of the alk product and didn't have the same elevated potassium problem I had. Which makes sense, but it probably should have been labeled as such. The Red Sea products are really easy to get, seem to be reliable, and their Ca based trace element line is nice and simple.

I think in time though, the Reef Blueprint might be a very good product line after it's fully developed and he ramps up manufacturing and distribution.

 

[Randy Holmes-Farley]

Ok, thanks for the info.