DIY Phosphate Dosing Solution (1 Viewer)

[Cody]

So I have struggled with low phosphates in the past and always dosed Brightwell's NeoPhos, which is great! I love their products, the concentrations are consistent, and the calculating equations they provide are accurate! However, you can cruise through them quickly and it adds up on larger/multiple systems. So, I purchased some dry powder a few months ago to make my own solution. Flash forward to today when I spent the time to try and dial in the proportions and how much it would raise the PO4 in my tank.

I have always used Green Leaf Aquariums nitrate powder to make my own dosing solution, so I figured I'd give their phosphate one a try as well. Brightwell NeoPhos raises the PO4 of 1 gallon of water about .25ppm, so I wanted a similar concentration, for a few reasons, that's easy to measure and mix. What I found is that 1/2 TSP (3 grams) of the Green Leaf PO4 powder mixed with one gallon (3.785 Liters) of RO/distilled water makes for a concentration that raises one gallon of water by .16ppm, which is great! It's significant enough to not have to dose a bunch, easy to measure and mix, and allows you a little more flexibility in situations where you need to raise it slower or have a smaller tank. Not to mention, a single $5 one pound bag can make about 115 gallons of dosing solution, versus the $11 for 500mL price for Brightwell.

The dosing calculation is this:

(ppm to raise parameter / .16) x water volume in gallons

That tells you how much to dose in mL. Pretty easy once you dial it in.

 

[Reefahholic]

Raising 1 gallon by .16 ppm PO4? How many mL’s of solution? That’s extremely potent! That means you’re raising 100/G by 16 ppm PO4.

I always mix mine dosing pump friendly to spread out the dose, and minimize impact.

For example…let’s say 5mL of solution will raise PO4 in 100/G by .02 ppm if the ppm increase needed is for moderate to high consumption. If the consumption is low you will want to make a more dilute solution so you can run out the dose further.

 

[Reefahholic]

Send me your water volume and I’ll make you a nice custom solution if you like.

BTW….I believe brightwell is using potassium phosphate as well. Probably the cheapest they can find off eBay. Sodium isn’t available anymore the last I checked.

 

[Cody]

Raising 1 gallon by .16 ppm PO4? How many mL’s of solution? That’s extremely potent! That means you’re raising 100/G by 16 ppm PO4.

I always mix mine dosing pump friendly to spread out the dose, and minimize impact.

For example…let’s say 5mL of solution will raise PO4 in 100/G by .02 ppm if the ppm increase needed is for moderate to high consumption. If the consumption is low you will want to make a more dilute solution so you can run out the dose further.

One mL of the solution raises a gallon of RO water by .16ppm, which is a lot less than the Brightwell does. I made it a little weaker for the same reason you mentioned, plus lower concentrations are easier to dial in.

To raise a 100 gallon tank by 16ppm you'd need to dose 100mL all at once. The reason I went with this concentration is that at first I was making it WAY too strong. So, I went with the smallest measuring spoon I had (1/2 TSP) and added it to 250mL of RO water. Still higher than the Hannah could read. Then, I added another 250mL at a time until I got to two mL of water per 1/2 TSP to even be able to measure. The 1L/1TSP ratio would raise a gallon of RO by .5ppm per 1mL dosing solution dosed. So, for easy measuring, I bumped the 1L of water up to 3.785L and called it a day.

That single bag of PO4 powder is a friggin lifetime supply!

 

[Reefahholic]

One mL of the solution raises a gallon of RO water by .16ppm, which is a lot less than the Brightwell does. I made it a little weaker for the same reason you mentioned, plus lower concentrations are easier to dial in.

To raise a 100 gallon tank by 16ppm you'd need to dose 100mL all at once. The reason I went with this concentration is that at first I was making it WAY too strong. So, I went with the smallest measuring spoon I had (1/2 TSP) and added it to 250mL of RO water. Still higher than the Hannah could read. Then, I added another 250mL at a time until I got to two mL of water per 1/2 TSP to even be able to measure. The 1L/1TSP ratio would raise a gallon of RO by .5ppm per 1mL dosing solution dosed. So, for easy measuring, I bumped the 1L of water up to 3.785L and called it a day.

That single bag of PO4 powder is a friggin lifetime supply!

Just make it to where you’re only raising your PO4 by .02 ppm in your total volume (in 24 hrs) for how many mL’s you want to dose. I’ve helped several people with their Brightwell dose and it’s much weaker than what you’re describing above. The formula is on the back of the bottle. It’s like 5-6 mL will raise PO4 by .02 to 100/G or something very similar to that.

Weigh your product in grams instead of using tsp. With Phosphate it takes very little compared to nitrate. So you need a scale that can get down to 1 gram accurately. On most tanks, 100-300/G they only need 1-3 grams to mix with 800-1000 grams of RODI.

 

[Reefahholic]

What is your total volume

 

[RR-MAN]

Start with dosing 1/4 of the recommended amount - I use the brightwell stuff

 

[Cody]

Just make it to where you’re only raising your PO4 by .02 ppm in your total volume (in 24 hrs) for how many mL’s you want to dose. I’ve helped several people with their Brightwell dose and it’s much weaker than what you’re describing above. The formula is on the back of the bottle. It’s like 5-6 mL will raise PO4 by .02 to 100/G or something very similar to that.

Weigh your product in grams instead of using tsp. With Phosphate it takes very little compared to nitrate. So you need a scale that can get down to 1 gram accurately. On most tanks, 100-300/G they only need 1-3 grams to mix with 800-1000 grams of RODI.

Yeah those calculations check out with the back of the bottle, and my solution is less than theirs. Also, I did include grams per water volume for the amount to mix. I have one of those fancy drug scales, baby! Haha! A 1/2 TSP leveled flat with a credit card is 3 grams of their powder.

For this particular tank, the water volume is about 125 gallons of true volume. I only dose 4mL to raise it .005ppm.

 

[Cody]

Start with dosing 1/4 of the recommended amount - I use the brightwell stuff

Yeah I would recommend that too for anyone doing anything dosing wise until they check after the dose and see what it did to your system. You can always scale up, but it's hard to scale down.

 

[Reefahholic]

One mL of the solution raises a gallon of RO water by .16ppm, which is a lot less than the Brightwell does.

For this particular tank, the water volume is about 125 gallons of true volume. I only dose 4mL to raise it .005ppm.

I’m lost! How does 1mL raise 1/G of RO by 0.16 ppm, but you’re dosing 4mL to 125/G and it raises by .005 ppm?

 

[Reefahholic]

Start with dosing 1/4 of the recommended amount - I use the brightwell stuff

If you dose .02 ppm daily it will always be safe. No guess work.

 

[Reefahholic]

@Cody So 16mL will raise 125/G by .02 ppm.

1mL will raise 125/G by .00125 ppm. That is a good weaker solution for low demand on dosing pump. On my GHL I could spread that dose out 150x daily.

 

[Cody]

I’m lost! How does 1mL raise 1/G of RO by 0.16 ppm, but you’re dosing 4mL to 125/G and it raises by .005 ppm?

So correct me if I'm wrong (not hedging, I mean literally correct me if my calculations are off so i can adjust my equations), but here is the calculating formula I use. I derived it based off the Advanced Instructions label on the Brightwell bottles, and the math seems to hold up. The key is knowing how much 1mL of dosing solution raises one gallon of water. For instance, I make my own calcium solution and 1mL of solution raises to one gallon of RO water by about 20ppm.

X= water volume
Y= ppm to increase
Z= mL to dose


Problem 1: The Ca solution increases one gallon of water by 20ppm. How much will dosing 120mL of solution to a 120 gallon system increase the calcium of the water volume in ppm?

X= 120 gallons
Y= ppm to increase
Z= 120mL


Y= (Z/X) x 20
Y= (120/120) x 20
Y= 1 x 20
Y= 20

So in this situation, the math seems to check out. If 1mL raises one gallon by 20, then dosing 120mL in a 120g system would raise the levels by of the system by 20mL. After all, 1mL raises one gallon by 20, so if you dose 1mL per gallon of water volume, then it should raise the whole system by 20ppm. Sound about right?



If the first equation is true, then this one should be true as well.

Problem 2: The Ca solution increases one gallon of water by 20ppm. How much will solution must you dose to increase in the system 20ppm?

X= 120 gallons
Y= 20ppm
Z= amount of solution to dose

Z= (Y/20) x X
Z= (20/20) x 120
Z= 1 x 120
Z= 120mL

Again, if there are 120 gallons of water, and 1mL of solution raises one gallon by 20ppm, then dosing then you'd need to dose 1mL for every gallon to raise the water volume by 20ppm.



Here's easier math for y'all none math nerds.

Problem 3: 1mL of dosing solution raises 1 gallon of water by 10ppm. You have one hundred 1 gallon buckets of water. You want to raise each of them by 10ppm total. How many mL of dosing solution should you dose?

 

[Cody]

@Cody So 16mL will raise 125/G by .02 ppm.

1mL will raise 125/G by .00125 ppm. That is a good weaker solution for low demand on dosing pump. On my GHL I could spread that dose out 150x daily.

Yes, that's correct. 16mL will increase your system by .02ppm and that whole equation thing I just posted was nothing more than an exercise in confirming my equations are correct haha

Having said that, I don't think that spreading it out evenly over the course of the day will achieve flat levels. If alkalinity is any indicator of coral growth, then using a calcium reactor with a Trident tells the story of when corals are growing in relationship to when the lights turn on and off. Coral growth is not constant throughout the day.

With everything stable and a Trident that tests four times a day, I have noticed a trend. My lights come on from 12pm-8pm. My trident tests at 12am, 6am, 12pm, and 6pm. 12am is lowest result of the day despite being 4 hours after the lights are off. Somewhere between 12am and 6am, the level starts to rise and is higher at 6am than 12am. The highest levels of the day are at 12pm when the Trident tests. It dips down by 6pm and reaches its low again at 12am.

Now, could the levels continue to drop after midnight? Sure. Could the numbers continue to rise after noon? Sure. But I do know for sure that by six hour after each one, the levels are moving in the opposite direction. If I had to guess (for alk dosing based off of when my lights turn on and off), I would imagine putting all my alk dosing between noon and midnight would be the best idea. It would make it more stable.

 

[Reefahholic]

You can always spread it out when you have the highest consumption rates, but I personally just spread it out over 24 hrs as I can spread out the dose more which is less hitting the water and less impact to the system/corals.

For example…if you’re dosing your 24 hr Kalk consumption only at night, you have to double the dose for that 12 hrs which is more of a spike to the system. This kinda seems logical in one sense because dosing opposite of the photo period should help increase pH at night when it dips, but then the spike to the water is more potent. Does it really help as much was we think? For the corals it may feel like an annoying slap across the face every time that dose hits the water which could potentially slow growth. For me I kinda feel like spreading it out is better no matter what the rate of consumption is through that 24 hr period. I could be wrong. Maybe the corals are thinking why are you trying to shove food in my face when I’m not hungry.

I think this is why calcium reactors work so well. It’s a steady stream 24/7 as opposed to 10-40 doses per day. Of course the steady stream is more stable with less impact on the system. It’s like this below:

CaRx: ———————————————

Pump: ^ ^ ^ ^ ^ ^

Which is more stable? The spikes or the stream.


Check your PO4 dose here:

James' Planted Tank - Dosing Calculator

You’ll have to work out the molar mass if not potassium phosphate. It won’t be too much off though. I know for TSP it’s like 77% as much as it calls for. So you would multiply the product amount in grams by 0.77 to get the actual product amount to mix with. We dose off of the actual change to the value anyway. So if the dose is too hot or too weak we just adjust the dose up/down. Not that big of a deal unless it’s waaaay off.