What's with the Kalkwasser sediment -- can it be reused?

[Dag]

There's a few issues here:

1) I have a 5 gallon dosing jug, to which I add 2 teaspoons of kalkwasser powder, and shake. Yet there always some significant residue on the bottom and it doesn't seem to fully dissolve, even though the amount I use is no more than recommended. Is this normal? Can I just add more fresh water to this residue, or should I throw it out?

2) I have the Osmolator, which works on the principal of adding lots of kalkwasser powder to a little jar through which top off water is pumped periodically. After a week or so, when I go to add more, I always notice powder clumped at the bottom, and I can't tell if this is powder that just didn't dissolve or is it the same residue I notice on the bottom of the Kent dosing jug. Same question: Can I just add more fresh water and shake it up (in effect reusing it) or is this bad stuff that should be thrown away?

Thanks, Randy.

[MargaritaMan]

Add more water, stir it up again, let it settle, drip clear water in to tank, do it all over...

I use a 20 g container and dump a couple cups in every month or so and do the same, works just fine.

MM

[Randy Holmes-Farley]

The solids can be undissolved calcium hydroxide that can be reused, but can also include calcium carbonate, magnesium carbonate and hydroxide, and other impurities that won't dissolve. AIt is OK to let it accumulate for a while, then toss it out.

These articles show some analyses and discission of the solids:

Magnesium and Strontium in Limewater
http://www.advancedaquarist.com/issues/dec2003/chem.htm

The Self Purification of Limewater (Kalkwasser)
http://www.advancedaquarist.com/issues/may2003/chem.htm

The Degradation of Limewater (Kalkwasser) in Air
http://reefkeeping.com/issues/2003-05/rhf/feature/index.htm

The best way to tell if the limewater is still usable (that is, acceptably potent) is by conductivity as shown in the last article above, but pH can also be used with less accuracy.

[Dag]

Randy, in Calfo's last coral propagation book, he suggested mixing up a highly concentrated cup of Kalkwasser and dosing at night in one shot (and not raising pH by more than .2). I confess that I have done this many times, adding this concentrated mixture in the sump. Have I done a terrible thing adding all of these "impurities" to the tank?

This is my favored approach when I realize my pH has dropped below 8.0 and I want to quickly raise it to 8.1 - 8.2. Must I stop?

[Randy Holmes-Farley]

I am not sure how much impurity is in most limewater, and it obviously will vary with brand, water source, etc.

Clearly some folks do it OK. But letting it settle adds some insurance, IMO.

How important it is to let it settle may also depend on other factors, like regularity of water changes, etc.

So I think it better to let it settle, but apparently not always necessary.

[Dag]

Thanks. You seemed only hesitant, not adamantly opposed, which is probably insufficient to make me change my practice.

[Randy Holmes-Farley]

:lol:

Sounds reasonable. I'll be more adamant when I need to. :D