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View Full Version : Dosing limewater - how much can you use at once


Frogmanx82
10/19/2009, 12:32 PM
Without a dosing meter, is limewater something that can be squirted in front of a powerhead once a day. Would that cause too much of a pH swing. I have a low demand 90 gallon tank so I would think a half oz would be all I would need per day.

bertoni
10/19/2009, 12:44 PM
A half ounce into 90g is unlikely to cause a problem, although I don't think it'd add very much alkalinity or calcium at all. You might see some precipitation of calcium carbonate, though. I think a slow drizzle would be fine.

Randy Holmes-Farley
10/19/2009, 12:59 PM
Adding the equivalent of 0.5 meq/l (1.4 dKH) in alkalinity all at once will boost pH by 0.6 to -.7 pH units instantly. That is likely too much unless the pH is very low to begin with.

Spreading it out over several additions would be better. That's why people drip it:

What Your Grandmother Never Told You About Lime
http://reefkeeping.com/issues/2005-01/rhf/index.htm

Frogmanx82
10/19/2009, 01:06 PM
Looking at the chemical calculator I would need almost a gallon of limewater to raise my calcium 10 ppm in a 90 gallon tank (figuring 70 net gallons). Hmmm...I'm thinking limewater is not for me. I think I need to go with a calcium chloride/baking soda/epsom salt method.

Now that I understand more of the chemistry, I'll be returning the purple up I got.

Now I just need to figure out how to determine how much iodine to add if any.

bertoni
10/19/2009, 01:07 PM
That sounds like a more reasonable amount, and that'd be unsafe to dose at once, in my opinion.

Randy Holmes-Farley
10/19/2009, 01:27 PM
Now I just need to figure out how to determine how much iodine to add if any.

That's easy. I don't see a need for it in most tanks unless you have certain gorgonia.

KevChem
10/19/2009, 02:29 PM
OK - I'm going to throw this out:

I add almost a liter of limewater to my 10gallon (+4 gallon "sump") tank every other day - all at once. Yes, I likely have pH swing (and salinity swing since that is my top-off).

I have not had any problems (precipitation or dead fish/corals).

YMMV and I'm not advising you to do something similar.

Kevin

Randy Holmes-Farley
10/19/2009, 02:55 PM
Assuming that is saturated limewater (is it?), that will create a huge pH spike.

Ever measure the pH after adding it?

KevChem
10/19/2009, 03:37 PM
Running the experiment right now (recording pH readings every 2 seconds).

KevChem
10/19/2009, 03:48 PM
OK - so here it is:

I placed a pH probe in the top front corner of the tank (lights off to eliminate interference). I have a HOB filter placed in the center back, which is where I add the limewater. The probe will not receive a direct flush of limewater since it is off to one side. I add the 800ml of limewater over about 1 minute time.

pH before addition of 800ml of limewater (pH=11.88) to 14gallon system: 8.32

The maximum pH reached was 8.45 and was reached after about 1 minute.

The pH oscillated plus/minus 0.03 units as it slowly drifted down (not sure why - about a 1-minute period per cycle. At 10minutes the pH was down to 8.42.

Extrapolating out, I'd say within a couple of hours (at most) I'll be back around 8.3

I'm still not saying this is fine for anyone else - just in my tank I haven't noticed any negative change in my inhabitants.

Kevin

Randy Holmes-Farley
10/19/2009, 03:50 PM
How did you make the limewater? I assume the pH is inaccurate at the pH (11+), or else it is very weak. Strictly by pH it is only 22% saturated.

KevChem
10/19/2009, 03:56 PM
I use a portion of lime (CaO - scientific grade) (not measured, but more than 1/4 cup) on the bottom of a 1L plastic bottle. I add RO/DI at a high rate to mix. I let it settle until I am ready to add it to the tank then I pour carefully from the top. The pH I state there is measured with a Vernier pH probe - I didn't calibrate that high, so no it might not be accurate. By wide-range pH paper it is about 12 as well, but it is hard to distinguish the blue/purple at the high end.

Randy Holmes-Farley
10/19/2009, 03:57 PM
To compare, you can make a slurry of limewater that will be a good pH 12.54 standard for comparison. :)