Introduction To Phosphates

[simonero]

This topic could fall under several categories so I chose to put it here.  Please move if necessary!
 
A recent tank emergency has gotten me curious about the facts regarding phosphates and how this nutrient affects the balance of a freshwater tank.  I'm also curious how this changes in a planted tank, about the relationship between phosphate and algae (especially green water and diatoms), and whether adding aragonite (or other buffers) too quickly can cause a phosphate imbalance (potentially spurring a tank crash).  I've tried to look these things up, but as a relative novice who has never thought about phosphate before it's a bit difficult to find the information I need to get started.
 
Any information related to those general topics, or answers to any of the specific questions below, is very appreciated!!!
 
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Some specific questions:
 
1. Do organic and inorganic phosphates affect a freshwater tank in the same way?
 
2. Are there ways to measure both, together or separate?  If separate, and purchasing both is not currently an option, what is the better starting point?
 
3. How do phosphate needs change in a planted tank?  Does this vary based on the type of plant?
 
4. What visible indications of phosphate elevation or deficiency present in a planted tank?
 
5. Does phosphate elevation or depletion cause algae?  If no, does it maintain algae?  (Please specify algae type.)
 
6.  Should phosphates and algae be addressed separately or concurrently?
 
7. Does adding buffers (e.g. aragonite) deplete or increase phosphate levels?  If yes, does that happen dramatically enough that buffers should be added modestly/gradually?  (in consideration of phosphate specifically; pH and kH obviously need to be monitored but those are well addressed in forums/literature)
 
8. What are the safest ways to influence phosphate levels for general maintenance?
 
9. What are the safest ways to influence phosphate levels for emergency maintenance?
 
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Again, answers to ANY of these are appreciated.  And if there is a comprehensive post somewhere that I missed, pretty please point me in that direction!  

 

[Akasha72]

Hi,
 
I'm not sure I can answer your questions specifically but I have had to learn a bit about phosphates recently.
 
I ended up with my tank blanketed in black beard algae. I even joked that it would grow on my fish if they stopped still long enough. I'd got to the point where my tank was such a mess that I was considering giving up fish keeping altogether.
It was then, when I was moaning about my tank to a staff member at Maidenhead Aquatics, that I was told about phosphates and what it can do when it get too high.
The staff member suggested I got it tested and sure enough, it was found to be excessively high in my tank. At this stage my fish were sickly and weak too and so I knew I had to do something about it. I set about finding out where it was coming from first, so I bought a test kit, re-tested my tank and then my tap water. I found out it was coming out of my tap at 1.6ppm - too high for fish keeping. 
I looked at various ways to reduce it but in the end I decided to run a remover perminantly. Several months down the line and I've just about got it under control. My BBA has gone - although I did buy 3 siamese algae eaters to eat it. 
 
I do have a thread running on here about it and one of the lads who has a marine tank has shared info about using vinegar to control phosphates. I've no idea if any of this is of any use to you but I thought I'd share anyway.
Here's the thread in case you are interested  http/www.fishforums.net/index.php?/topic/440296-struggling-with-high-phosphates-again/

 

[StevenF]

Many of your questions will be hard for me to answer definitively.  Mainly because phosphate exists in many different forms in the aquarium.  It will exist linked to organics materials or as an oxide PO2PO3,PO4, or PO5.  Some may be very soluble in water and others will not.  So some will exist as a solid in the substrate while the rest may be dissolved in water.  Some will be acidic and will lower PH while other forms will not affect PH.  Many of the insecticides and pesticides we use today consist of organic molecules linked to Phosphate.  So I have to assume that some of the phosphate in a aquarium may be toxic to fish.
 
As far as I know most test kits only measure PO4.  So I would have to assume that there will be some in your aquarium that cannot be detected by the tests.  I haven't seen any other test kits that detect other forms of it.  I purchased an API test kit partially because I had an algae issue that I couldn't resolve after over a year. I had hair, spot, and film algae and at least one I cannot identify.  When i first checked the water with my test kit I got 5ppm.  I had to do a lot of water cycling and substrate vacuuming to to get it down but it wouldn't stay down.  I then tried phosphate remover and that did work.   As the phosphate levels dropped the algae slowly diminished.  The little bit I have left is now manageable with water cycling and by changing how long the light stays on. My test kit now tells me I am around 0.5ppm and possibly very close to zero.  Unfortunately the API test kit is very difficult to read below 0.5ppm.  And it is my understanding that most natural places in the world have very low levels of phosphate.
 
I have since managed to modified my plant fertilization routine to so that I am adding everything the plants need except phosphate.  I am using RO water so I have to fertilize it.  Otherwise my plants will die.  Now with improved lighting, and more aeration plant growth is fast enough alone to keep the phosphate levels low.   Before I got the fertilization right  my PH was close to 8 and GH was about 75ppm.  Once the plant growth accelerated PH dropped to 7 in less than a week and GH is now about 25ppm. KH also took a substantial drop but I don't remember what it originally was. The change was quite sudden and worrying but nothing died.
 
I think the safest way to manipulate phosphate levels is by water changes, manipulating plant growth and using a phosphate remover. Also different plants grow at different rates so some will soak up more phosphates than others.  I have also been adding Calcium carbonate and magnesium carbonate for some time.  Without it my shrimp would not be able to molt and would die.  Overall I cannot say that calcium or magnesium made any noticeable difference in phosphate.  But adding sea shells or aragonite to your aquarium is the best way to insure adequate KH and buffering to your aquarium. The only obvious signs I had of high phosphate before I tested for it.was algae and suppressed plant growth.  

 

[Far_King]

. The only obvious signs I had of high phosphate before I tested for it.was algae and suppressed plant growth.  

 
This is exactly what I'm seeing occurring in one of my tanks.  My PO4 reading was around the 1ppm mark, so not excessively high, but my plants are suffering and the BBA is growing on my bogwood.
 
I've switched fertiliser, trying different lighting times and i've added some Rowa Phosphaway into my cannister filter.  
 
I had this occur in another tank of mine ages back, and a combination of Amano shrimp and SAE beat the BBA into submission.  This then allowed my plants to re-stablish and I'm sure that then has allowed the tank to get back into balance as the plants thrive and algae is nowhere to be seen.  
 
This occurred after a substrate change for me.  I'm certain the key is getting the plants to absorb the nutrients the BBA would feed on thus denying it the chance to grow.  I may have to find some smaller SAE's for this tank.

 

[StevenF]

 
 
I do have a thread running on here about it and one of the lads who has a marine tank has shared info about using vinegar to control phosphates. 

My understanding was that he was using the vinegar as a substitue for CO2.  While most plants only use carbon from CO2 some can use organice compounds in water just tlike CO2.  his idea is to increase the carbon available to accelerate plant growth in the hope that would soak up the excess phosphate in your water.   
 
Did you try that?  Did it work?  I would like to know how that works out if you tried it.  

 
StevenF, on 15 Feb 2016 - 11:20 AM, said:

. The only obvious signs I had of high phosphate before I tested for it.was algae and suppressed plant growth.  

 
This is exactly what I'm seeing occurring in one of my tanks.

Please note I recently have read that excess potassium can also result suppressed plant growth.  And my own experience I have learned that not having enough of one micro nutrient (in this case copper) can also suppress plant growth.  So just suppressed plant growth by itself doesn't indicate an excess imbalance is pressent.