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post #1 of 18 (permalink) Old 10-25-2011, 04:56 AM Thread Starter
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Phosphate question

Hello everybody. I've been having really hard time growing plants. So I finally got the master test kit and I've started to do some serious testing in last 6 weeks. I've been testing about 2x a week and each time I test my nitrates are really low and my phosphate level reads 5+. I did some internet searching, and I found out that the reason why my plants are doing so poorly may be high phosphate levels. In last 6 weeks I've been dosing only nitrates, potassium and micros (nitrate, potassium mo-we-fri, micros tue-thu-sat, water change sunday) I don't use any carbon in my filter, I feed really small amounts of food and I don't have co2 system. After weekly 30-50% water changes in my 20G, my phosphates still read high (5+). I tested our tap water and it reads almost 0 phosphates. I've started to look into phosphate removers, but I'm not sure what is the best way to go here. I have coralife 65w bulb turned on for 7 hours each day. I don't really have big algae problems. I have hair algae mostly growing on my moss, but it doesn't grow out of control. Any ideas?
Thanx.
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post #2 of 18 (permalink) Old 10-25-2011, 08:13 AM
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Hi Roadrunner, welcome!

My phosphate test consistently reads 10+. But if I go by the test results and stop adding more, I soon see phosphate deficiencies in the plants, as well as green spot algae that indicates low phosphate.

I've tested the test, by mixing up solutions of phosphate and distilled water of known concentrations, and all those read perfectly. And it reads 1ppm with my tapwater, which I've verified with the water company is also correct. It's only with real tank water that I get results which are totally at odds with what's happening in my tank. It's a mystery I've never been able to explain.

I've been told many times never to put too much faith in tests. And I'm forced to agree. It's not a very satisfying answer, but that's the way it is.

Even if you really do have 5ppm of phosphate, that's usually not a problem. Granted, I have seen reports from people who had persistent algae problems, who found relief only with phosphate removers. But that's a fairly rare occurrence. Furthermore, most of these people usually have at least 3ppm of phosphate in their tapwater. That phosphate is in the form of orthophosphate, rather than the potassium phosphate we dose; and it seems to have different effects on a tank.

Chances are your problem lies elsewhere. In particular, your light/carbon ratio. At 65W, that sounds like a power compact (PC) fixture. I'm no good at estimating light levels for those, but I'm fairly certain that you'll have enough light that your plants require some form of supplemental carbon.

If you have high light, you need CO2; no way around it.

If you have medium light, CO2 will still provide the best plant growth. However, Seachem Excel is also an option. It doesn't provide nearly as much carbon as real CO2, but it can provide just enough at this light level to keep plants healthy, add to growth a fair amount, and prevent algae. Although it's not recommended if you keep anacharis or hornwort, and vals may suffer until they adjust.

If you tell us the distance between the bulb and substrate, hopefully someone with PC experience can tell if you have medium or high light.

Then, you'll need to decide whether to reduce the light level to low, or add either Excel or CO2 as necessary. DIY yeast CO2 is quite feasible on that size tank, if you don't mind mixing up some new yeast/sugar mix every week.

Once the light/carbon ratio is right, then we can work on the fert requirements; which will of course change along with changes in light/carbon.
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post #3 of 18 (permalink) Old 10-25-2011, 01:59 PM
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5+ is not a lot. If you does using EI dosing, you need carbon source. CO2 or Excel. Mine is hovering consistently at 5ppm. My nitrate is between 35+ down to 10.
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post #4 of 18 (permalink) Old 10-25-2011, 02:06 PM
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Quote:
Originally Posted by DarkCobra View Post
Even if you really do have 5ppm of phosphate, that's usually not a problem. Granted, I have seen reports from people who had persistent algae problems, who found relief only with phosphate removers. But that's a fairly rare occurrence. Furthermore, most of these people usually have at least 3ppm of phosphate in their tapwater. That phosphate is in the form of orthophosphate, rather than the potassium phosphate we dose; and it seems to have different effects on a tank.
Yes, they add Orthophosphate in tap water to prevent corrosion.
Orthophosphate means phosphate in inorganic form.

But, KH2PO4 = Potassium Dihydrogen Orthophosphate

Same thing.


roadrunner, it took quite long (1-2 months) for me to bring PO4 down from
5 PPM to below 0.5 PPM. There might be lot of it in the substrate, apart from
fish load. More light will help plants take it up quicker (we are talking
about reducing the phosphate, not high light = more algae subject, aren't we?).

More NO3 too, in case the slowness is from NO3 deficiency.

So that you can see it yourself if controlling PO4 works for you or not.
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post #5 of 18 (permalink) Old 10-25-2011, 02:27 PM
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Oh, I would recommend Phoslock for phosphate removal. Get them here:
http://www.bigalspets.com/Magnavore-.../dp/B00176GT8I

They aren't cheap.
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post #6 of 18 (permalink) Old 10-25-2011, 02:56 PM
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Roadrunner, I would be more concerned with your low levels of nitrates. Given in combination with the high phosphates, I say your issues is not enough nitrates. However, can you give us readings on all your parameters? I had a 20G with the exact same light and had to dose some nitrogen, phosphates and potassium along with micros. I got by without co2, but I had algae in places. Usually when your nitrates are low in a planted tank, the phosphates just sit there as there is a relationship. Get your nitrates up and they will be able to utilize the phosphates.

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post #7 of 18 (permalink) Old 10-25-2011, 03:30 PM Thread Starter
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Thanx everybody for helpful answers. Actually I have already started to dose extra Nitrates. They usually read 5-10. I do have small amount of green spot algae on the glass, but not very noticeable. I used to have lot more on my anubias, not so much lately. CO2 is definitely on my list. I was trying to dose excel in the meantime but I have some plants in my tank that can suffer from it. My windelow was constantly having brown leaves, after I stopped dosing phosphate and dose more nitrates and potassium, it looks better.
I was wondering, until I get CO2, would it help if I cut down on the light time?
thanx
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post #8 of 18 (permalink) Old 10-25-2011, 03:43 PM
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Absolutely! Remember, light drives the need for co2 and nutrients. Cutting light will indeed help. Try just an half-hour at a time, do it slowly and go back if the plants start to suffer. I got by with a 4 hour period on my setup that was like yours, but generally had it on for about 5.5 - 6 hours a day. You could also try just dosing 1/4 the excel every few days and slowly working your way up.

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post #9 of 18 (permalink) Old 10-25-2011, 06:05 PM
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Quote:
Originally Posted by KH2PO4 View Post
But, KH2PO4 = Potassium Dihydrogen Orthophosphate

Same thing.
This is true! But there still seems to be some correlation between high phosphates in the tapwater and algae, that doesn't seem to occur when dosing large amounts of KH2PO4.

What's probably in tapwater is phosphoric acid, and I have successfully induced algae using that.

I don't mean to dissuade the OP from trying phosphate level reduction and seeing what the effects are. But if there are other issues, they should be solved first; so you can see the effects of phosphate level without interference. And phosphate adsorbants should definitely be the last resort, due to their cost.
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post #10 of 18 (permalink) Old 10-25-2011, 06:35 PM
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Have fun with Green Spot Algae when you start your phosphate reduction.

I dose a full tsp of KH2PO4 on my tank every other day. This is a little over 19ppm of phosphates just from dosing for my super-high-light-high-co2-high-nutrient-experiment tank. Less than this and I get enough GSA to wreck my HC carpet in a few days.

I'm not 100% algae free just yet, just waiting for the GDA to go away now that I've reduced my (over)feeding.


EDIT: I think DarkCobra's post is spot on for roadrunner's issue.
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post #11 of 18 (permalink) Old 10-25-2011, 11:18 PM Thread Starter
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Quote:
Originally Posted by DarkCobra View Post
This is true! But there still seems to be some correlation between high phosphates in the tapwater and algae, that doesn't seem to occur when dosing large amounts of KH2PO4.

What's probably in tapwater is phosphoric acid, and I have successfully induced algae using that.

I don't mean to dissuade the OP from trying phosphate level reduction and seeing what the effects are. But if there are other issues, they should be solved first; so you can see the effects of phosphate level without interference. And phosphate adsorbants should definitely be the last resort, due to their cost.
And that's why I'm here looking for other option and leaving chemical removal as my last resort. I guess I should leave it as is or I could cause more algae outbreaks. First I'll try cutting down on light. Maybe do couple of shorter periods during the day and see how that goes. Thanx

I had lots of fast growing plants like hornworth, java fern, moss and I've got message from local plant guru:
"I suspect that your plants are causing your nitrates to bottom out releasing phosphates as a fertilizer uptake by product.
I know it sounds convvoluded, but all the plants you have have the potential to be nitrate sponges."


I got rid of the hornworth, but I kept everything else + added more slower growing plants to help with phosphate reduction. It's been only one week, so I can't tell if it made much difference yet.

What are your thoughts?

Last edited by roadrunner; 10-25-2011 at 11:20 PM. Reason: spelling
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post #12 of 18 (permalink) Old 10-26-2011, 07:08 AM
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Sounds like your plants are getting Nitrogen-limited. Just up your nitrate dosing, which will then allow the plants to grow and use up more phosphates.

Also, what exactly do you mean by having a hard time growing plants? Are they dying or just doesn't seem like growing at all?
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post #13 of 18 (permalink) Old 10-26-2011, 07:32 PM Thread Starter
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By hard time growing plants I mean that they grow really slow, my windelow had leaves that quickly turned brown. Blyxa japonica lost all leaves in short period time (they were all floating around tank) and even managed to "kill" hornworth! My nitrates always use to read around 5-10 before and I never used to do the phosphate test until about two months ago when I got master test kit. So since then I started to dose only potassium and nitrates. I have eliminated dosing KH2PO4. Plants seem to be doing much better. My plants leaves don't turn brown as quickly or as many as they did before.
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post #14 of 18 (permalink) Old 10-26-2011, 08:24 PM
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Agree that most of your plants are nitrate sponges. Not sure if plants can release phosphates in response to nitrates bottoming out as your local guru suggests, but they can definitely stop uptake of other nutrients if any one bottoms out.

Some extra nitrate would probably be a good thing. Don't neglect the light/carbon issue though.

A few comments on individual plants, just to rule out other errors:

Blyxa japonica loves CO2. I'd go as far as to say it's really a requirement for good results. It's actually a very short stem plant, and seems to die off if it's buried deeply enough in the substrate that the majority of the stem is also buried.

Java ferns cannot have their rhizome buried at all, or they'll die. Best to tie them to a rock or driftwood.

Hornwort is tricky to add to a tank, keeps falling apart, and doesn't really produce roots. Keep replanting the largest fragments, eventually it will take hold. Hardy once it does. Doesn't like Excel.
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post #15 of 18 (permalink) Old 10-26-2011, 09:11 PM Thread Starter
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Thanx DarkCobra
I did changed the light settings last night. Now I have 2 hours in the morning and 4 at night. Plus I added little excel before lights went on this morning and see what happens. I've been dosing extra nitrates 3x a week and I'll move java. I have nice piece of wood that I can attach the plant to.
I guess i'm getting CO2 for x-mass. I would like to have some HC growing in my tank and I know it's a must for that.
I won new ADA Do!aqua 17G tank that I'm thinking to start properly with substrate, CO2 and everything. It will probably make my life lot easier.
From your experience, what substrate is the best?
Thanx
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