Newbie chemistry Q's on Ca and KH

[ron101]

Hi, I have been keeping reefs for about 6 months. Up till recently I have been using a 2 part regimen for maintaining KH and Ca levels but have had difficulty raising pH over 8.0 during the day. I have now switched to using Kalkwasser but I don't have a great understanding of the big picture.

More specifically some questions I have are:

- Are products such as Seachem Reef Advantage or Kent Turbo Calcium a form of calcium chloride?
- Do these products tend to deplete alkalinity and lower pH hence requiring corresponding KH buffer additions?
- Will a CaCl + KH buffer regimen result in increased salinity or ionic imbalances over time due to accumulations of Cl and Na ions?
- When using Kalkwasser are additions of KH buffers also required or is it a 'stand alone supplement'?
- What is the whitish precipitate that collects at the bottom of a kalkwasser container? Is it harmful if any escapes into the tank?

TIA

[Randy Holmes-Farley]

ron:

Are products such as Seachem Reef Advantage or Kent Turbo Calcium a form of calcium chloride?

Yes to Turbo Calcium. The Seachem product is similar but has strontium and magnesium in it. From the Seachem web site:

Reef Advantage Calcium™ also includes magnesium and strontium in amounts proportionate to typical utilization ratios (100:5:0.1, Ca:Mg:Sr). This allows one to maintain these two important elements while maintaining calcium.

Do these products tend to deplete alkalinity and lower pH hence requiring corresponding KH buffer additions?

They do nothing to supplement or deplete alkalinity. You'll need to do that some other way.


Will a CaCl + KH buffer regimen result in increased salinity or ionic imbalances over time due to accumulations of Cl and Na ions?

Yes, here are a couple of articles:

http://www.animalnetwork.com/fish2/aqfm/1998/dec/bio/default.asp

http://www.animalnetwork.com/fish2/aqfm/1999/feb/bio/default.asp


When using Kalkwasser are additions of KH buffers also required or is it a 'stand alone supplement'?

Stand alone. Many use no other additives at all.

What is the whitish precipitate that collects at the bottom of a kalkwasser container? Is it harmful if any escapes into the tank?

It is largely calcium carbonate and/or calcium hydroxide. It is preferable to send neither to the tank. It contains impurites from the Ca(OH)2 and the CaCO3 can result in precipitatiopn of additional CaCO3 and MgCO3 from the tank water, possibly reducing calcium and alkalinity.

[tyoberg]

Randy always does a good post. I'd like to add one small thing, cause I think it would help.

Everything in you tank is made of CaCO3--calcium carbonate. Snail shells, LR, SouthDown or other aragonite sand, coralline, coral skeletons. Coral, coralline and other inverts make their structures by taking both calcium and carbonate out of the water. For every Ca++ ion used, one CO3 ion is also used. Since alkalinity is really a way of measuring carbonates, this explains why both calcium and alkalinity tend to drop and why both may require supplementing.

[ron101]

What is the whitish precipitate that collects at the bottom of a kalkwasser container? Is it harmful if any escapes into the tank?

It is largely calcium carbonate and/or calcium hydroxide. It is preferable to send neither to the tank. It contains impurites from the Ca(OH)2 and the CaCO3 can result in precipitation of additional CaCO3 and MgCO3 from the tank water, possibly reducing calcium and alkalinity.

So then limewater may not simply be a pure calcium hydroxide solution but also has some carbon content? Im somewhat confused about where any carbonate comes from a theoretical Ca(OH)2 + H2O equation.

[Randy Holmes-Farley]

It comes from the air!

Carbon dioxide (CO2) hits the water, forms carbonic acid (H2CO3), gets deprotonated to CO3--, and the carbonate precipitates with the Ca++.