When I do my weekly 50% water changes, I don't add any extra Equilibrium to bring my dGH up toVaughnH;19187 said:Tom's EI formula is for maintaining the Ca and Mg in the tank as the plants use up what is there. Then, when you do the 50% water change you add back for the lost Equilibrium you dumped with the water...

__X__dGH. My tap water already has ~ 1.7 dGH in it when I add the water back. I just continue the normal dosing like I do every day.

I am taking into account the 5 gallons of water that is drained and replaced daily.VaughnH;19187 said:...In my case I dump about 11% of the Equilibrium every day, due to my constant 5 gallons per day flow into/out of the tank. So, it seems to me that I need to add about 11% of the original dose of Equilibrium every day to make up for that. I think that's where our difference comes from.

The 0.675 grams or ~ ⅛ teaspoon of Equilibrium daily is based on 45 gallons and not 40 gallons. It does include the 5 gallons that is replaced daily plus the 40 gallons that is in the tank; hence the 45 gallons. If you weren't using the 5 gallons replaced daily, you would use 12.5% less daily. This would be dosing 0.59 grams daily. These amounts are based on the fact that Tom's formula calls for 25 grams mixed with 1 liter of water and dosed at 12 mL per 20 gallons. As you can see, it's a very small amount of Equilibrium that is added daily.

If you want to dose more than this or less than this, then your dosing amount will certainly be different.

Using this equation, what is your target dGH and how much will you be dosing daily? What will you be using for the time interval?VaughnH;19187 said:...The "Dilution equation" I use is from Wikipedia and is: natural logarithm[final Concentration divided by initial concentration] = Flow Rate divided by total volume times the time interval. (all with consistent units).

Hoppy, would you mind providing the link in Wikipedia for that dilution equation? I've been looking, but I haven't found it. It's almost 3 AM here and my eyeballs are getting crossed.

That particular equation is not in my lab math book and I'd like to read about it.

Thanks!

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