# Phosphate power can not be underestimated



## scuba guy (Feb 10, 2007)

For weeks now (months), I have had trouble with my Amazon swords. Green, kind of healthy - but little growth - and I would see brown spots and 'holes' develop in the leaves - small not a big deal. I didn't understand what was going on. My tiger lilies also behaved the same way.

My nitrate levels were constant at 10 ppm - which I also didn't understand - I have a high light, high CO2 aquarium with pearling and my Nitrates were constant. I attributed this to the 10 angelfish I have and my high protein food. But I have read here suggested that fish alone are not enough to add Nitrogen.

But something just wasn't right.

My phosphate tested at .5 to 1.0 ppm - which I thought was fine. I am deathly afraid of algal blooms - algae can make a mess of your tank. My tap water has about 1.0 ppm in the supply. I change water weekly (about 25%) and when I tested my aquarium I had some phosphate so I thought that was good. So I never added phosphate .... hmmm... could that be my problem?

I decided to do a test - I added Phosphate. Enough to bring the level up to 1.5 to 2.0 ppm.

And WOW. Over night my nitrates dropped to zero. OVER NIGHT. I haven't noticed any growth to speak of yet since I just did this - but I wonder..... 

I wonder if I had been phosphate limited all this time. I had no insight that Phosphate would control nitrate uptake (true?) and utilization. In a tank loaded with nitrate, and potassium and all the trace minerals needed with plenty of light and CO2, the plants were starving for Phosphorus - and without it. they use much less of the other nutrients ?

Apparently the phosphate from my tapwater was not enough - 

If I get an algal bloom - I'll live with brown spots - though


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## dennis (Mar 1, 2004)

If you added PO4 from KH2PO4 you may have had a K deficiency. The brown spots and holes in leaves does not sound like a PO4 but rather a K issue.

Also, how sure are you of your test kits? Have you calibrated them?


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## Laith (Sep 4, 2004)

:-D

I think it was the phosphate. Dennis, see this thread where scuba guy describes a bit more in detail the plant issues he's having:

http://www.aquaticplantcentral.com/...ants-discussions/37882-fertilizer-review.html

I don't think raising PO4 by 1mg/l using KH2PO4 will add enough potassium to fix a potassium limited situation...


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## scuba guy (Feb 10, 2007)

I believe I have plenty of Potassium. I fertilize using GW's Potassium. In fact, I probably add on the higher side as K is not toxic in high dose.

The Phosphate, however, I had never added - relying instead on my tapwater. But I don't change water that often - so I suspect that may have been limiting. 

Tapwater source is probably fine under a lower light/no CO2 injection situation, but not in my case.

In any event, I have my aquarium under test. I'll let you know how it proceeds.
It's 10:30 a.m. and all my lights are on - significant pearling is starting to kick in. It will be interesting to see if my plants clear up their 'spots' and grow taller.


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## Laith (Sep 4, 2004)

Don't let those Nitrates stay bottomed out!


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## scuba guy (Feb 10, 2007)

Just added them this morning - level is at 10 ppm. It will be interesting to me to see how long that level holds. It dropped pretty fast once I added Phosphate.

Interesting hobby.


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## dennis (Mar 1, 2004)

Your right Laith, that does not add much K does it <blush>. I missed that other thread too, thanks. Well, then the evidence certainly could point to a PO4 limitation though the brown spots sound like something else to me.


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## Leonard (Mar 4, 2007)

I been av´bout the same thing. I've got tuftalges (they some when you have CO2-shortage), and when I added more mikronutrient, they haven't come back yet =)


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## scuba guy (Feb 10, 2007)

*Phosphate update*

Well...I've learned something. There's a reason why Phosphate causes green water - plants love it.

I have avoided adding Phosphate to avoid algae assuming my tapwater was sufficient (1.0ppm). But not so. Nitrates stayed stuck at 10 ppm , etc.

So I added phosphate three days ago expecting an algal bloom. Didn't happen

Instead my Nitrate plummeted to near zero...added more nitrate, and overnight fell back again. Only since adding PHosphate (to 1.5 -2.0 range) did my nitrate begin to fall.

And...my plants after 3 days are showing renewed vigor....especially the Amazon's. I suspect Potassium is getting sucked up too, but I have no way to measure - so I add when I add nitrate.

I do believe I was phosphates limited. Whatever phosphates were in the water were getting quickly scarfed up. The algae can't compete with my heavily planted tank.

My aquarium calls for 2.0 ppm to be maintained in order for High light and High CO2 to work effectively. This is new to me. I thought 1.0 was sufficient.

Thanks all for the help in the other threads.


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## Laith (Sep 4, 2004)

As opposed to the amount of potassium in KH2PO4, there is more potassium in KNO3. For example, adding about 10mg/l of NO3 using KNO3 will also add about 6.5mg/l of K.

Some people have reported that an excess of potassium has caused them issues though I never had problems when I was adding K2SO4 in addition to KNO3.

Now however I rely only on the K that is added when I dose KNO3... seems to be more than adequate for my plants.

To be kept in mind if you're using KNO3 to add the NO3  ... maybe cut back a bit on the extra potassium dosing.


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## scuba guy (Feb 10, 2007)

will do on the K.


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## simpsota (Mar 11, 2006)

scuba guy said:


> For weeks now (months), I have had trouble with my Amazon swords. Green, kind of healthy - but little growth - and I would see brown spots and 'holes' develop in the leaves - small not a big deal. I didn't understand what was going on. My tiger lilies also behaved the same way.


So Scuba, how do the swords look now?

I'm having the exact same spot/hole issue with my swords. My test kit says I've got ~3-5ppm PO4, but I haven't calibrated it so I don't really believe it. If you've found the holes are stopping I may try upping my PO4 by a ppm or two to see if it helps.


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## yildirim (Nov 25, 2004)

According to my past experiences and tests, I believe that (this may sound weird to you but) PO4 defficiency is never the cause for any damages (like holes or decoloring). It is most important and disregarded (because its measured quantity is always the lowest) macro in the water column which effects:
1. Take up of all other nutrients; if you are po4 limited you can not expect your plants to use all N or K in the tank. If kept high plant growth and use of all available nutrients will be easier resulting better and healthy growth.
2. It is the most imp part of the balance in the tank; small changes in the levels of other nutrients doesn't make big changes while the effect of changes in po4 level is incredible and in a very short time you can observe defficiencies of any kind of other nutrients.
3. PO4 is never the cause of an algea; in fact not having all nutrients in abundance causes algea, and keeping po4 elevated usualy dismiss the most common algal problems.
So what I always did in my tanks has been to keep PO4 levels high (around 5ppm) with daily dosings of all nutrients.


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## Bert H (Mar 2, 2004)

> 1. Take up of all other nutrients; if you are po4 limited you can not expect your plants to use all N or K in the tank. If kept high plant growth and use of all available nutrients will be easier resulting better and healthy growth.
> 2. It is the most imp part of the balance in the tank; small changes in the levels of other nutrients doesn't make big changes while the effect of changes in po4 level is incredible and in a very short time you can observe defficiencies of any kind of other nutrients.
> 3. PO4 is never the cause of an algea; in fact not having all nutrients in abundance causes algea, and keeping po4 elevated usualy dismiss the most common algal problems.


Nicely put, Yildirim!


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## scuba guy (Feb 10, 2007)

A comment on my swords.

It's been a week or so since I 'upped' my PO4. And sure enough, the swords look better. The new leaves are not developing holes. I don't have the fantastic growth I was looking for, but at least the new leaves are healthier looking.

I concur on the limiting nutrient part of this thread. I am trying to get my 'ratios' correct so that I don't have any limitations. I do add csm+B now that I received a supply from GW.

Some observations.

I don't have any algae problem. I have high light (4x96 watt on 65 gallon) and high CO2 (pressure supply- constant/PH monitored)
My nitrate stays between 5-10 ppm - I haven't had to add any.
I do have 10 medium breeding size angels which are fed blood worms/Krill and other high protein foods almost daily). They are fed well.

My baby tears cover the bottom. They grow like weeds (I cut them back evey week) and look great. I keep them low to the substrate and the high light helps keep them 'running'. My Tiger Lily behaves like my Amazons; Look good don't grow very much. My crypt melted. My ludwigia is RED with big large petals. It is growing well, but older leaves seem to green out and die off. Root hairs are all over the plant stems - looks neat. Val giants develop very wide leaves, but brown out towards the top. I cut them back once a week. My java fern sucks. It is attached to driftwood and I see attempts at growth, but it looks terrible. 

In all, my aquarium is completely covered in plants, very little substrate visible. I do use fert tabs under my Amazons and tiger lily. Helps get iron to the plant I suspect since the plants greener now. 



I don't know if my fish are the reason why my Nitrate stays up.


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## DJKronik57 (Apr 17, 2006)

I tried adding PO4 to my tank to see if it would improve growth and instead got an outbreak of green dust algae all over the glass. I stopped dosing PO4 and the green dust algae disappeared. Didn't notice any significant increase in plant growth, and the plants grow fine without it for me. Test kit said I had around 1.0ppm before I started adding it. 

I don't think saying PO4 doesn't cause algae is correct...ANY nutrient can cause algae if not balanced correctly.

Any thoughts as to why my tank behaved the way it did when I added PO4?

29 Gallon, 180W, 8hr period
Dosing nitrates, potassium, and trace elements 3 times a week
Excel with water changes once a week, DIY CO2


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## Laith (Sep 4, 2004)

DJKronik57 said:


> ...
> 
> I don't think saying PO4 doesn't cause algae is correct...ANY nutrient can cause algae if not balanced correctly.
> 
> ...


Yes, but it's not that PO4 itself that is causing the algae outbreak but, as you yourself mention, it's an *imbalance* of nutrients (including light and CO2 by the way).

In your case I would venture to say that you haven't found that balance in your tank. You have 6.2wpg over your tank, which is a lot of light. While DIY CO2 may be possible on a 29g tank, with that much light I'd have trouble keeping the CO2 where I want it and consistent.

Also with that much light (and good plant mass), you may be under dosing some/all of your macros and micros. But if you have growth issues, I'd first sort out your light/CO2 relationship...


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## eklikewhoa (Jul 24, 2006)

I think with that much light and diy co2 is the main problem....


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## scuba guy (Feb 10, 2007)

My CO2 is not DIY. It is a pressurized monitored system. I flow CO2 to maintain between 20-30ppm with a Kh=11. My Ph ranges 7.2 to 7.4 during the day. (lower at night, etc.). I have plenty of CO2.


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## eklikewhoa (Jul 24, 2006)

scuba guy said:


> My CO2 is not DIY. It is a pressurized monitored system. I flow CO2 to maintain between 20-30ppm with a Kh=11. My Ph ranges 7.2 to 7.4 during the day. (lower at night, etc.). I have plenty of CO2.


Ooops, I meant my reply to be directed to DJkronic


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## SnakeIce (May 9, 2005)

The only draw back to high K is inhibited Ca and Mg uptake if K levels are much above Ca levels. 

You should have a 4-1 Ca-Mg ratio with K not being higher than Ca levels to optimize these three nutrients.

If you have hard water with high Ca, you will have to dose extra K and Mg because the higher levels of Ca will inhibit the other two nutrients unless those two are also higher.


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## scuba guy (Feb 10, 2007)

Interesting - SnakeIce ....

I have hard water here in Houston. Kh varies between 11 and 15 (right now it's at 11, but as summer approaches it goes up)....so lots of Ca Co3.

When I use 2X96watt lights I don't have any 'pearling'. With the two additional 96 watt lights, the plants pearl.

Since adding the additional Phosphate, I do notice a little more algae on the glass (not much more, just noticeable). The Amazons 'seem' to be a bit better (no brown spots anymore), but they are not thriving .

I am beginning to think it is just competition between plants. My Ludwigia is putting out lush new growth, but the older leaves are dying off and dropping....so it looks kind of top heavy.

Maybe I should vary the light intensity during the day....low light most of the time and then full light for two hours ....


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## dennis (Mar 1, 2004)

kH is not necessarily an indication of Ca levels. A high kH means you have lots of carbonates/bicarbonates in the water but they do not have to come from a Ca source. The only way to know for sure ow much Ca you have is to do a Ca hardness test. The only way to know how much Mg you have is to do an accurate Gh and Ca hardness test, then compute the Mg from that (or do a Mg test). The Only way to know your K levels is to work for someplace that has really nice electronic testing equipment.


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## Laith (Sep 4, 2004)

eklikewhoa said:


> Ooops, I meant my reply to be directed to DJkronic


Mine too!


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## kaaikop (Mar 22, 2005)

Wow, interesting thread, I am going through a very similar experience here...
trying to figure out how come my nitrates are not coming down, while Fe and PO4 levels (1.0 ppm) are dissapearing overnight. I will try boosting it up to 2 ppm (any issues with Iron being at 2 ppm (using GSM+B as iron source)?


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## simpsota (Mar 11, 2006)

scuba guy said:


> Maybe I should vary the light intensity during the day....low light most of the time and then full light for two hours ....


I've got two bulbs so I have one come on (about 30 minutes after my CO2) at 10am. At 1pm my second light comes on giving me high light levels. Three hours later at 4pm the first light switches off leaving me back at the one bulb light level. Three hours later at 7pm the second light bulb (and CO2) shuts off. That way I have 9 hours of light with three hours of "mid-day like" light in the middle of my light cycle.

That takes three timers including the one for the CO2, but even the digital timers are pretty cheap at Target... [smilie=b:

I start the light at 10 so that I can have it on longer in the evening...


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