View Full Version : Dosing Randy Holmes-Farley's Recipe for Calcium

Blue Ring Sting
09/15/2013, 06:41 AM
Hi All

I am interested in making on Randy's recipe for Calcium. The ingredients and recipe is fairly simple but the problem I am having is not knowing how to dose with recipe 1. Please see below:

Recipe 1:

Dissolve 500 grams (about 2 1/2 cups) of calcium chloride dihydrate (Such as Dowflake 77-80% calcium chloride) in enough water to make 1 gallon of total volume. You can dissolve it in about 1/2 gallon of water, and then pour that into the 1 gallon container and fill to the top with more fresh water. This solution is then about 37,000 ppm in calcium.

If you use an anhydrous calcium chloride (such as Kent's Turbo Calcium or Peladow Calcium Chloride (a brand sold by Dow that some believe may just be a dehydrated equivalent of the Dowflake), then you should use about 20% (1/5) less solid calcium chloride to make the recipe. Note that the solution will get quite hot when dissolved anhydrous calcium chloride.

As you see this recipe contains only 37 000 ppm in calcium whilst Seachem and other calcium dosing products contain between 160 000 and 110 000 ppm.

Also the dosing directions are fairly self explanatory depending on your level of experience, as with Seachem for example they say that if you dose 5 ml of Reef Calcium you will raise your calcium levels by 3 mg/L.

So my question is basically how do I dose Randy's recipe? Has anyone had experience with this? If I use 5 ml to dose what sort of change will I have in calcium levels in my aquarium?

All help will be appreciated.

09/15/2013, 06:51 AM
Here is a good calculator, just fill in the blanks and select the supplement of your choice in the drop down menu.


Blue Ring Sting
09/15/2013, 11:13 AM
Thanks downbeach. I have that calculator, it shows me what the total amount of calcium additive needs to be added but it is not accurate to say a cap full. It shows that you need to add a total of 54 ml for example and shows that you can dose it in 2 portions. You can dose 1/2 or 1/3 then check the next day and add the rest.

Is that safe? If the change is to increase calcium by 20ppm can that be done in 2 days with any negative affects?

09/15/2013, 05:04 PM
20 ppm can be dosed in one shot safely. Two days would be okay, too, although the tank might consume 10-20 ppm per day, depending on the growth rate.

Blue Ring Sting
09/16/2013, 12:30 PM
Currently I have an empty tank with heater, wave maker and substrate. I want to test the calcium levels in the tank and then add a 5 ml of Randy's calcium formula and see what the change would be.

I want to see how much the ppm levels will increase with a dosage of 5 ml. Since there will be nothing using the calcium in the empty tank I am sure the reading will be accurate.

09/16/2013, 12:39 PM
How big is this tank? 5ml of calcium part may not make enough change for you to be able to notice on your test kit.

For example, in a 100gallon tank, 5ml of Randy's Recipe calcium part will only change the calcium level by 0.5ppm. You'll never ever be able to see that on your test kit.

09/16/2013, 12:40 PM
In a 10gallon tank the change would be 5ppm, still not enough to see.

I guess if the tank is 1 gallon or so, then 5ml is a sensible plan.

Otherwise, you could skip this whole experiment and just do the math.

Blue Ring Sting
09/16/2013, 01:02 PM
Thats what I am struggling to find out. The tank is about 25 gallons ( 100 l ), I would like to make a formula for myself for dosing. I just want to find out what each capfull will do to an aquarium. For example Seachem directions are:

Add 1 capful (5 mL) per 80 L (20 gallons*) twice a week. You can increase the amount or frequency based on growth response but do not exceed 3 capfuls per 80 L (20 gallons*) per day. Each capful will raise calcium by about 3 mg/L.

How would I be able to calculate what 5 ml of Randy's recipe will do?

Blue Ring Sting
09/16/2013, 01:08 PM
Is it possible to test the formula on RO water? I did a test this afternoon and it shows the following:

Calcium - 30 ppm
Phosphate - 0
Magnesium - 0
Alkalinity - 0.6

If I dose calcium can I use this as a positive reading or would I need to test it on saltwater to get an accurate reading?

09/16/2013, 01:14 PM
You can use that, but you have to figure for the volume. How much 2-part into how much RO water?

Why are you afraid of math? C1V1 = C2V2.

If you have a 100L tank, then that is 100000 ml


37000ppm * 5ml = xppm * 100000ml

Solve for x and that is how much 5ml of calcium part will raise the tank.

Or just use the calculator referenced in the second post of this thread. If you know that you need 54ml to raise calcium by some amount then just do the stupid math and figure out how much 5ml would raise it. It's simple division, not rocket surgery.

Blue Ring Sting
09/16/2013, 01:26 PM
I will need to do the calculations.

I am not afraid of math just math is not a strong point of mine. I prefer to use trial and error methods and work out the how much calcium will make how much of a change in a fixed amount of water.

All of my tanks are 100 l so I will need to calculate how much will have what sort of effect on 100 l.

09/16/2013, 01:29 PM
37000 * 5 / 100000 = 1.85

5ml gets you 1.85ppm in 100L

I can understand math not being a strong point, but we're not talking about hard math. Simple multiplication and division. Stuff you can do on a calculator.

Doing this by trial and error you have to start considering the error in the test kit, the error in the volume measurements, etc. etc. etc. and you end up with a measurement that you can't be sure if you can trust.

Take your previous example, what if that 30ppm was really 25? It might have been. Most test kits wouldn't be able to tell you the difference between 25 and 30ppm. That would throw your dosing off by 15%!

Doing this with math gets you the right answer in less than 10 seconds.

Blue Ring Sting
09/16/2013, 01:33 PM
Ok when you do it like that it looks extremely simple. I appreciate it. I am on the reef chemistry calculator now busy working it out for different volumes.

Blue Ring Sting
09/16/2013, 01:38 PM
The formula provided seems fairly simple and more accurate than trial and error. I didnt understand the previous formula provided but from what was explained now my understanding is much better.

Blue Ring Sting
09/21/2013, 12:02 PM
If I dissolve 1 kg of calcium chloride dihydrate to 1 gallon of water instead of 500 grams, will the ppm be 74000 ppm instead of 37000 ppm?

09/21/2013, 12:45 PM
If I dissolve 1 kg of calcium chloride dihydrate to 1 gallon of water instead of 500 grams, will the ppm be 74000 ppm instead of 37000 ppm?

If you can get it to dissolve.

Blue Ring Sting
09/21/2013, 12:50 PM
What would the problem be with getting it to dissolve?

09/21/2013, 11:02 PM
Well, it's going to reach saturation at some point. I am not sure that 74,000 ppm is possible with hobbyist equipment.