Today on the BRSTV 52 FAQ should you mix your kalk ?
Hi I'm RT turner your host of BRSTV’s 52 FAQ.
Today we are answering k mam’s question.
“hi, you mention that we should not mix the solution after it has been mixed, but
certain reactor like Two Little Fishes has stirrer that works with ato which will stir
the solution once ato is on..
“ We are going to answer this question as well as some general thoughts on kalk reactors.
This is a pretty common question and at face value it is absolutely confusing because almost
all of the advice out there tells you after you mix the kalk and fresh water once leave
it sit and do not mix it again.
However all the kalkwasser reactors out there do just that very thing, constantly mix the
solution or at least do so many times a day.
The answer lies within how the kalkwasser is implemented in the aquarium which in a
vast majority of cases is mixed in a container and slowly dripped into the tank or added
via an auto top off.
When using an auto top off or DIY dripper the kalkwasser or calcium hydroxide powder
should be thoroughly mixed with freshwater once and once only and then put a lid on the
container to limit gas exchange.
Mixing it the first time allows the calcium hydroxide to fully dissolve into a solution
of ionized calcium and and hydroxide ions.
Once it’s fully mixed its often referred to as a fully saturated solution meaning there
is as many calcium and hydroxide ions dissolved in the water as their ever will be.
After that mixing it won't make any additional kalkwasser dissolve into the solution, in
fact the opposite will happen.
When you mix it you add atmospheric carbon dioxide into the solution from the surrounding
air in the room.
When the carbon dioxide enters the solution it reacts with the hydroxide in the water
to form carbonate which in turn reacts with the calcium to precipitate out as calcium
carbonate which reduces the available calcium and carbonate in the solution so it is no
longer fully saturated.
.
So simply put mixing doesn't make the solution more concentrated it potentially makes it
less potent and needlessly wastes raw material.
best thing you can do is put a lid on the container and leave it alone.
Doesn't need to be a hermetically sealed lid , just one that limits the amount of fresh
air inside the container.
In fact, when left alone the saturated kalk solution will form a crust on the surface
which essentially protects it from carbon dioxide exposure.
Ok so why do all the reactors mix it constantly or several times a day then?
The answer that is fairly simple , they are small containers which are constantly fed
new freshwater.
With the previous solution you are often mixing up enough fresh water for anywhere from an
entire day to week or even month.
With most kalk reactors they only hold enough water for a portion of the day and the nature
of their design is they feed the saturated kalkwasser solution into tank by pumping freshwater
into the bottom of the reactor which forces saturated kalk water out of the top.
Meaning that freshwater that enters the bottom does need to me mixed, Since there is no air
inside the reactor mixing it also won’t cause precipitation issues or dilute the potency.
One note, the saturated kalk solution is fairly clear and that is what you want to dose.
The milky white solution is what we commonly refer to as a kalk slurry.
This slurry contains not only saturated kalk solution but also undissolved or suspended
calcium hydroxide particles.
This slurry is way to potent to dose to the tank, if you do the PH swings will be immediate
and large.
we would strongly recommend against dosing the slurry to the tank.
Open and honest I have a hard time recommending kalk reactors in most cases.
In theory they will keep the solution 100% saturated but a container with a tight fitting
lid performs almost as well without the expense or hassle.
Some reefers believe they save space but you still need a container to hold the freshwater
so you are actually loosing space when you add the reactor into the mix as well as adding
more equipment into the mix which can fail.
It's been our experience simple and reliable is what produces long term successful reef
tanks.
that said some of us are gear junkies and knowing the mixture is 100% saturated to the
max is important so we do have some advice on selecting a proper kalkwasser reactor.
There are basically two types.
mixers and stirrers.
the mixers will turn on a pump for a few minutes to periodically mix the kalk into a slurry
and then turn off to let the particles settle out leaving only the saturated kalkwasser
solution behind.
Problem with these is you need a series of timers to make sure the system never doses
the kalkwasser until after the kalk as settled out otherwise you end up dosing the undesirable
slurry.
This can certainly be done but has a lot of opportunity to fail and frankly the saturated
kalk is really hard on the pumps.
Two little fishes also makes small mixer which works off the feed pump.
This certainly works but you get what you pay for so don’t be shocked if the stir
mechanism clogs and finding the right flow balance where it is properly mixing but not
sending slurry into the tank can be somewhat challenging.
Frankly I also don't think it holds enough kalkwasser powder to be particularly useful,
to maintain full saturation most tank owners would have to fill it pretty frequently.
The type I have used in the past and recommend if you are in the market for a kalk reactor
is known as a stirrer which uses a slow moving bar at the bottom to keep the kalk constantly
mixed and fully saturated.
The stir bar moves slow enough that the slurry stays at the bottom and the saturated kalk
solution goes to the top.
When you pump in new fresh water it enters the bottom and has to pass through and mingle
with the constantly rotating slurry at the bottom.
as long as you pump water through the reactor slowly and in periodic bursts the slurry stays
at the bottom.
Aquamedic makes a pair we most commonly recommend.
In most cases we find that investing in the larger of the two is wise because the large
capacity makes it much easier to prevent the slurry from reaching the top and being dosed
to the tank.
That wraps up today's 52 faq, If you are interested in learning more about kalkwasser in general
and how it works checkout Week 30: Kalkwasser: An All-in-one Calcium, Alkalinity & pH supplement.
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