View Full Version : New alk supplement

04-07-2011, 05:24 PM
Is anyone here using the new Coral Grow additives?

I switched to baking soda for my dKH a while back and I'm kind of lazy so I've been playing around with concentrations to minimize the number of times a month I need to make new solution and with baking soda I could dissolve about 3.5 cups in a gallon of warm water. 4 cups and it would super-saturate and spontaneously precipitate like snow when the water cooled off to room temp (clogging my dosing pump in the process).

I just switched to my first bag of the Coral Grow bicarbonate additive and started off with 3 cups per gallon. After 10 minutes of mixing it was the consistency and colour of a melting milkshake, with a thick, grainy foam. Even diluting it by half wasn't enough to make it dissolve completely.

After 24 hours my 1.5 cups/gallon solution of the Coral Grow on the same dosing volume as my 3.5 cups/gallon baking soda has actually increased my alkalinity by 0.3 meq/L. That's actually great as I can extend the life of one batch of solution, but I'm a little confused. I thought bicarbonate was bicarbonate? How is baking soda so much less concentrated? Am I missing something fundamental here?

04-08-2011, 07:28 AM

Just sent you a pm.


04-08-2011, 11:55 PM

Hopefully this info will answer your question. To start off I will try to explain a few things:

Sodium bicarbonate reaches saturation at 18c(standing water at average room temp) with the addition of 203.81 grams per litre. At 35c(warm water) the amount is 309.5 grams per litre.
~This figure was extrapolated from the Solubility in Water values on the Wiki site for Sodium Bicarbonate. Those figures are: 103gr per litre at 0c, 693gr per litre at 100c.

There is 3.78litres of water in a gallon

Therefore Sodium bicarbonate reaches saturation in 1 gallon of water at 18c by adding 770.4 grams, at 35c it takes 1169.9 grams. To allow a safety margin so we don't waste Sodium bicarbonate through precipitation it would be best to only add 725 grams/gallon at 35c. The higher temp would aid in dissolving and then the mix would not precipitate as it cooled.

Coral Grow Alk, Aluminum free weighs 302 grams/cup, thus by adding 2.4 cups to 1 gallon of RO water at 35c the solution is near saturation when it cools.
~you must tap the measuring cup several times while filling it to get this weight. I tapped it every time I added a heaping tablespoon to the 1 cup measure. If you don't tap the measuring cup you can be off by 30 - 40 grams.

By adding water to the sodium bicarb while it was cooling you were able to prevent more from precipitating out. Your concentration was probably higher than the one that had fully precipitated out. Hence the increase in Alk that was noticed.

Coral Grow Alk takes a little more effort to dissolve since it is not chemically made. When mixing in 84 grams per liter(balling method) the mix is transparent.

Hope this answered your question.


04-09-2011, 12:05 AM
Wow, that was brilliant, thank you!

I actually just ordered a high grade food scale, so I should be able to make near saturated solutions precisely following your recipe.

Again, thanks!