Adding Lime

saleen385 · Dec 31, 2016

I have a 180G mixed reef tank with a 40G sump that is about half full. So I'm estimating about 200G total tank water. My ALK is 84ppm, measured with a Hanna checker. I have 10G for auto top off. My PH was 7.8-8.0. How much lime should I add to the top off water? Have pickling lime.

Thanks,
Jim

Cory · Jan 2, 2017

Lime (calcium hydroxide) isnt a good choice to raise alk if thats what your doing. Because it raises ph too much if added quickly. But if you add lime to be able to maintain that alkalinity id start with 1/2 a teaspoon per gallon of top off water (not tank water). And see if it can keep up.

84ppm on the hanna checker is 4.8dkh. If thats correct you should boost it up to 7-11dkh with baking soda (sodium bicarbonate). You can buy it in the grocery store.

Something like 50 grams of it for 200 gallons of tank water will boost your alk to approximately 7dkh safely.

Once your alk is normal via sodium bocarbonate id then dose lime via top off, i wouldnt dose it all at once, it raises ph too much.

wkscott · Jan 2, 2017

You may be overestimating your total water volume. If you have about 20 gallons in your sump, that would mean that you have about 180 gallons in a 180 gallon tank. If you have any live rock and/or live sand in the tank, this is not possible. You want to be more accurate with your estimate so that you don't overdose.
For example, my sump has 14 gallons water in it (a 30 gallon sump.) I have a 90 gallon tank. I have 60 pounds of live sand and 100 pounds of live rock. When I set this tank up, I carefully measured the exact amount of water I put in (not my first tank so I knew to do this.) My total water volume is 80 gallons. I measured and weighed everything at set up so I would be more accurate with my dosing, especially for pH and alkalinity.

Randy Holmes-Farley · Jan 3, 2017

Add the top off water very slowly. You can add up to 2 level teaspoons per freshwater gallon. Maybe start at half that or less.

This calculator shows how much full strength limewater has how much effect:

http://reef.diesyst.com/chemcalc/chem_calc3.html