Can anyone please help me figure out these fert dosing miscalculations? - The Planted Tank Forum
 
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post #1 of 7 (permalink) Old 07-04-2005, 05:46 AM Thread Starter
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Can anyone please help me figure out these fert dosing miscalculations?

First, I started with these water readings from my tank:

PO4 = .5 (my tap water has .5ppm, so this is baseline for me)
NO3 = 0
K = Dont have a test kit, but Im assuming 0 because I didnt add any at all



Next, I did some reading to determine what I would need to add to hit my target levels. I used the directions on the bottles, and cross-referenced them with the info on rexgrigg.com's Fertilizers page (Rex's site has helped me incredibly). My target levels here are 10ppm NO3, and 1.0ppm PO4. You can check the formulas below at seachem.com

Here's what the bottles say to dose:

Nitrogen bottle says - .25 * 45 (gallons, my water size) * 10 (desired increase in ppm) = 112mL (amount needed to raise to that level)

Phosphorous bottle says - .8 * 45 (gallons, my water size) * .5 (desired increase in ppm) = 18mL (amount needed to raise to that level)

So I checked out Rex's site, and the dosing he posted for PO4 matched what the Flourish Phosphorous bottle said exactly. However, according to his caculation, for Flourish Nitrogen, I would only need 22.5mL to reach my target level of 10ppm (whereas the bottle formula works out to 112mL). This is a huge difference, and Im wondering where the discrepancies occur. However, I figured to do the smaller 22.5mL dose (since I trust Rex, and also, it's easier to add more if I needed to).




Then, I dosed my tank with:

22.5mL of Flourish Nitrogen
18mL of Flourish Phosphorus
60mL of Flourish Potassium
(And Flourish Trace, Flourish, and Flourish Iron - don't think this matters, but I did do it)


I waited 1:15 hours and then tested my water for a follow-up to my ferts dosing:

PO4 = 5.0 ?!?!? WTH?! o_O
NO3 = 5.0
No2 = 0



Questions I know will be asked:

1) I use the same test kits Ive always used (Aquarium Pharmiceuticals), and they've always been reliable.
2) I am 100% sure I added the correct amounts. I was meticulously careful.
3) I have a 55gal tank with pressurized CO2. pH = 7.0, KH = 6, GH = 2. No chem buffers or other additives.



So... here's what I need help with guys: Why are my Nitrates HALF of what I want them to be, and why are my phosphates 5x MORE than what I want them to be?! I about had a heart attack when I took the Phosphates reading LOL Where did I go wrong? Bad math? Can anyone help me sort this out?

~ Thx all for your time
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post #2 of 7 (permalink) Old 07-04-2005, 12:43 PM
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You should follow Seachem's printed instructions. You should not overdose their liquid products. Until someone from Seachem says different, I would assume that all or their liquid products contain the same preservative as Flourish Potassium. (Yes, that poster only complained of a problem with FW mussels, however if overdosing kills them I imagine it can't be good for the other livestock.)

I am not sure why you are overdosing Phospate when your levels are already at .5. You don't need to dose any.

Double check your instructions for Seachem Nitrogen. It's a blend of different Nitrogen sources, including ammonium, guanidine, and potassium nitrate. You should double your nitrate reading (per the label). Again, I personally believe you should not be dosing it higher than the label specs.

I personally believe the best way to add nitrate and phosphate to a tank is to simply add more fish. Keep the tank fully stocked, and the tank's cycle will produce all the nitrate you need. Most all fish food contains phosphate, so you are dosing phosphate every time you feed your fish.
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post #3 of 7 (permalink) Old 07-04-2005, 01:35 PM
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Quote:
I personally believe the best way to add nitrate and phosphate to a tank is to simply add more fish. Keep the tank fully stocked, and the tank's cycle will produce all the nitrate you need. Most all fish food contains phosphate, so you are dosing phosphate every time you feed your fish.
I keep seeing you say this and I'm really worried about it. If someone is running a higher light tank with CO2 injection there is no way that any amount of normal or even above normal fish load can keep up with the nitrate and phosphate needs of a decent amount of plants. Sure if all the plants are Anubias, Java Fern, and Java moss it MIGHT be able to. But if you have stem plants in there it's not going to happen. Unless you seriously over feed the fish. And fish food is more expensive than bulk ferts.

I also find it very strange that you seem to be about the only person I have seen on the net giving this advice.
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post #4 of 7 (permalink) Old 07-04-2005, 05:08 PM Thread Starter
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Rex, scold him later - help me! :p

just kiddin man, but seriously - any idea on where I went wrong? I used your page and checked and rechecked everything before I actually added anything.

OK, I understand that with .5 PO4 tap water, I prolly dont need to dose any phosphates until they are used up. Point taken.



Quote:
Originally Posted by Hypancistrus
You should follow Seachem's printed instructions. You should not overdose their liquid products. Until someone from Seachem says different, I would assume that all or their liquid products contain the same preservative as Flourish Potassium. (Yes, that poster only complained of a problem with FW mussels, however if overdosing kills them I imagine it can't be good for the other livestock.)

I am not sure why you are overdosing Phospate when your levels are already at .5. You don't need to dose any.

Double check your instructions for Seachem Nitrogen. It's a blend of different Nitrogen sources, including ammonium, guanidine, and potassium nitrate. You should double your nitrate reading (per the label). Again, I personally believe you should not be dosing it higher than the label specs.

What are you talking about man? I didnt overdose anything. I followed the FORMULA ON THE BOTTLE. Go to the website and read the bottle label yourself. And 1.0ppm phosphates (the target I was dosing for) is perfectly acceptable in a high light tank.

For the record, I have no fauna in the tank other than trumpet snails and 2 siamese algae eaters.
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post #5 of 7 (permalink) Old 07-04-2005, 05:26 PM
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If you are using a nitrate test kit then you need to multiply your reading my 2X as it states on the Seachem website. Also note this line on the Seachem website

Quote:
(if using a “nitrate equivalent” value for “n” then use a factor of 0.05 instead of 0.25 in the formula)
That is what I based the dosing on.

As for the phosphate.....maybe your test kit is wrong? Have you tested the test kit?
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post #6 of 7 (permalink) Old 07-04-2005, 06:46 PM Thread Starter
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So Im using a "Nitrate Equivalent" here? And I'd need to use the .05 constant? OK, deal. Also, I picked up on the "double your nitrate value" thing late last night too. Guess that solves that one.

Now the phosphates is still what is most mysterious here. I suppose I need to get a second opinion on my PO4 test kit ASAP.
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post #7 of 7 (permalink) Old 07-05-2005, 02:44 AM
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Quote:
Originally Posted by cgcaver
What are you talking about man? I didnt overdose anything. I followed the FORMULA ON THE BOTTLE. Go to the website and read the bottle label yourself. And 1.0ppm phosphates (the target I was dosing for) is perfectly acceptable in a high light tank.
I'm referring to the "beginner dose." I just don't know how "safe" Seachem products are past this based on that thread I linked. I guess I would say to just use caution. Especially since you have invertebrates.

As to the phosphates, it's just my own opinion that .5 is enough. If it were me I would follow the "beginner dose."

If you want to raise phosphates based on a formula, I would look to using mono potassium phosphate (KH2PO4), which you could get from Greg Watson. Let me work out some math for Phosphate... you would add 5.4242 milligrams of KH2PO4 per gallon of water to raise PO4 by 1 ppm.

Now this assumes 0 impurities, and the whole "impurity" argument recently came up here and caused a MAJOR controversy. Bottom line, the way I see it, Greg Watson sells agricultural grade, which is the cheapest and is fine according to a lot of people with a of experience. If it bothers you, you could buy "reagent acs" grade which is purer but will cost a lot more. So far, there are no hard numbers (meaning no lab tests with numbers showing percent of impurities, etc.).

Back to your tank.. if it is spec'd at 45 gallons, the water content will be less depending on how high your water level is, how much gravel/substrate you have, etc. I would probably calculate for 40 gallons. So, to raise phosphate by 1 ppm for 40 gallons, you would add .22 grams of KH2PO4. Since your levels are already at .5, you would instead add .11 grams. (Note this is a very little bit!) Verify with a test kit and add more or less depending on the results.

To weigh this stuff, you would want to use a "lab balance." You could search eBay to get one at less cost.

I would agree you might want to try another Phosphate test kit since your numbers are not matching the Seachem label. Seachem sells a nice one that's quick and easy to use and is quite accurate. You could go with a Lamotte kit if you want something that's considered more accurate. If you still get inconsistencies I would suggest asking the question on the Seachem Support Forum.



Quote:
Originally Posted by Rex Grigg
I keep seeing you say this and I'm really worried about it.
If you are so worried maybe you should add me to your ignore list. I specifically said that this is only my belief based on my testing and results ("I personally believe..."). I never said, "Everyone should do this because I am right and everyone else is wrong."



Quote:
Originally Posted by Rex Grigg
If someone is running a higher light tank with CO2 injection there is no way that any amount of normal or even above normal fish load can keep up with the nitrate and phosphate needs of a decent amount of plants.
Well guess what.

My lighting is 250W Metal Halide. That's high lighting.

I'm densely planted, lots of fast growing stems - cabomba, egeria, alternanthera, lysimachia, at least a dozen stems each. My cabomba grows about a foot per week. Plus I have crypts, swords, valis, and anubias. I actually use a separate anaerobic nitrate filter to lower nitrates. Doing all this, my nitrates stay between 10-20 ppm all the time. And I simply did it by adding more fish. I've verified it on several test kits. As to phosphate, I feed my fish every other day. My tank's phosphate levels usually always stay around 1 ppm, and again I verified this on multiple tests. Yes, I put more food in, because there's more fish! I invite anyone to look at the ingredients on their fish food, and I'm willing to bet you'll see phosphates listed! By the way, I usually only need to buy new food every 6 months or so.



Quote:
Originally Posted by Rex Grigg
I also find it very strange that you seem to be about the only person I have seen on the net giving this advice.
Excuse me? What are you implying? If you wanna accuse me of something, just come right out and say it!

All I have done is post what I've learned so far in the hobby. If you increase fish load and feeding, you get more nitrate and phosphate. Simple! It is working for me... I use RO water, so my phosphates are not coming in via tap. I change 40-50% water weekly! I wouldn't say this unless I believed it!
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