# Phosphate dosing w/ the Fertilator to fix GSA



## acbaldwin (Nov 3, 2005)

So I've had GSA on the glass of my tank for a while now, no complaints about and is easy to scrape off of the glass. Last night I saw that it was starting to get a foothold on my oldest sword, so I've gotta fix it. I knew PO4 was the solution and already have been dosing PO4 (via Kent Botanica PO4) every so often, with absolutely no scientific or exact approach. I might as well be making a witches brew. Anyways I decieded to start getting serious and checked out the algae finder, it suggested raising PO4 to 2 mg/l. I *think* that mg/l is equal to ppm, but am not sure. Assuming I was correct, I entered the info into the Fertilator. Here are my results:








~8,000 ml's seems a little excessive to me:crazy: . What's wrong here?
Thanks,
Andrew


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## Left C (Jun 14, 2005)

I think that the answer should be 88.5947 ml. This part of the fertilator seems to be off by 100 times what is actually needed. A percentage error calculation probably. Go back to the first part of the fertilator and plug this number in and you get exactly 2 ppm phosphate.

I tried this part of the fertilator using Seachem's products and got wierd answers too.


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## Phillyman (Dec 2, 2004)

Remember you want to dose for the actual gallons of water in the tank.I think the rule of thumb is to multiply the tank size by .85. So 55 x .85= 46.75, so I would dose for 45 gallons. If you have an extra deep gravel bed or a lot of rocks or decorations you can dose for a little less.


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## acbaldwin (Nov 3, 2005)

Okay, I took both of your suggestions (thanks!) and plugged them in.
At 45 gals approx water volume, I need to dose 72.42 mls. Isn't that still quite a bit?
If I dosed through dry KH2PO4, I would only need .49 grams. Is Botanica PO4 really that diluted?


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## Left C (Jun 14, 2005)

You should do as Phillyman says and base your dose on the amount of water in your tank. I get the same answer as he does but I use a slightly different equation. Let's say that your 55g tank is 20" tall with 3" of substrate and the water is to the top. So:
55g X (20" - 3") / 20" = 46.75g.

I can't tell you about Botanica products strength because I use Seachem's products.


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## acbaldwin (Nov 3, 2005)

I figured b/t 45-50 gallons (not much hardscape), tried a few to see the dosing range. I also tried calculating the dosing for Flourish PO4, and it's about the same. So, Left C, do you dose that heavily??


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## Left C (Jun 14, 2005)

acbaldwin said:


> I figured b/t 45-50 gallons (not much hardscape), tried a few to see the dosing range. I also tried calculating the dosing for Flourish PO4, and it's about the same. So, Left C, do you dose that heavily??


I dose about 0.5 ppm 3X a week and the rest comes from the fish food. I have Greg Watson's ferts so I'll be switching over soon.


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## acbaldwin (Nov 3, 2005)

So what is the actual dosing amount (in ml) that you put in to achieve .5 ppm? How big of a tank?
Thanks,
Andrew


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## Laith (Sep 4, 2004)

Here's a good calculator that calculates concentrations/dosing for commercial products:

http://www.fishfriend.com/fertfriend.html

There are 3.78 liters in a gallon...


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## Left C (Jun 14, 2005)

Laith said:


> Here's a good calculator that calculates concentrations/dosing for commercial products:
> 
> http://www.fishfriend.com/fertfriend.html
> 
> There are 3.78 liters in a gallon...


I like the fertfriend but I wish that it would show the potassium amounts in Seachem's Nitrogen and Phosphorus. It only lists the nitrate and phosphate amounts.


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## Salt (Apr 5, 2005)

Please forgive my ignorance, but what is the reasoning that adding a lot of phosphate to the tank will get rid of green spot algae?


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## banderbe (Nov 17, 2005)

Left C said:


> You should do as Phillyman says and base your dose on the amount of water in your tank. I get the same answer as he does but I use a slightly different equation. Let's say that your 55g tank is 20" tall with 3" of substrate and the water is to the top. So:
> 55g X (20" - 3") / 20" = 46.75g.
> 
> I can't tell you about Botanica products strength because I use Seachem's products.


Unless your substrate is solid, that doesn't account for all the water that is below the top of the 3" substrate.

I don't know if it would matter but I'm sure there has to be at least 2 or 3 gallons of water in the substrate. Particularly absorbant substrates would have even more.


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## John S (Jan 18, 2005)

i like chuck gladds calculator


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## Left C (Jun 14, 2005)

banderbe said:


> Unless your substrate is solid, that doesn't account for all the water that is below the top of the 3" substrate.
> 
> I don't know if it would matter but I'm sure there has to be at least 2 or 3 gallons of water in the substrate. Particularly absorbant substrates would have even more.


That's true that there's usually water in the substrate but many people have fish, critters, rocks, decorations, wood and such in their tanks. You have to account for this somehow. Someone else used "the 15% guess." I guess that works too. We both got the same answer. I think my formula takes a little more into account to figure out the water volume.

Unless you can remove all your water out of your tank somehow, all you can do is to take a "best guess" approach to calculating how much water is in your tank. My method is quick and easy to understand and use to approximate the water volume. Plus, if you do have a deeper or shallower substrate, finer or coarser substrate or even a lot of rocks and such, you can adjust this simple formula up or down as needed. Sometimes a "best guess" is all you can do.

If you have a better way, I'd like to know it.


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## Left C (Jun 14, 2005)

Salt said:


> Please forgive my ignorance, but what is the reasoning that adding a lot of phosphate to the tank will get rid of green spot algae?


There's plenty of articles about this approach. Sometimes it sounds a little odd considering the many phosphate removers on the market.

I did a search for "green spot algae" and this is just one of the many articles here about this pesty stuff. http://www.aquaticplantcentral.com/forumapc/showthread.php?t=12264&highlight=green+spot+algae

I hope this helps a little.


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