Phosphates

I know pretty much precisely zero when it comes to the subject of phosphates in an aquarium...  But then I read this posting from another forum: 

Hi I'm new here so I've only just read this article.  I'm really, really surprised that you don't mention phosphates anywhere in this otherwise excellent article.  Phosphates are the number one cause of algal blooms in the environment and, I believe, the smoking gun behind much of the algae problems in aquaria.  Many people struggling with algae in a tank fixate on killing the algae.  We know this is the wrong way to look at it.  Firstly, it is impossible to eradicate algae, their spores are everywhere.  Secondly, algae will subside all by themselves if you address the root cause which of course, you try to point out with lots of good suggestions.  It is common to blame nitrates and lighting but this is only part of the story.  What you really need to know is why your plants have stopped growing.

Nitrates, lighting, CO2 etc cannot cause an algal bloom without the presence of phosphate.   You can have a tank with ridiculously high nitrate and 10 watts per gallon lighting but if there are no phosphates, nothing will happen because no algae can grow without phosphate.  Conversely, Cyanobacteria can grow in the absence of nitrate because they can use nitrogen gas dissolved in the water.   

Phosphate is naturally present in extremely low amounts in healthy watercourses and plants have consequently become superb scavengers of phosphate.  Add phosphate and plants will at first greedily take it up and grow faster.  But in the fish tank, the levels tend to insidiously rise way beyond the needs of the plants, unless you have no/very few fish or do sufficient water changes with phosphate free water.  Even worse, and apparently much less well known, excess phosphate will eventually stop your plants growing because it interferes with iron uptake.  Your plants will gradually go yellow, especially the new leaves.  At this point, some people looking at the symptoms will suspect a deficiency and perhaps fertilise the tank.  Increasing available iron might help a little but ultimately, it's futile.    Growth will slow and eventually leaves will start dying.  Even more nutrients will be released into the water as they do so. (Note that iron uptake in plants is complex and all sorts of things can interfere with it, not just excess phosphate).

It is when your plants have stopped growing actively, the trouble really starts.  Algae tend not to do well in the presence of healthy plants.  But once the balance tips, opportunistic algae, which seem not to have the same problem with high phosphate, will start to take hold.  You'll start to see them growing on the leaves of your plants.  It is natural to blame the algae for the dying plants but it's actually the other way around.  But address the phosphate problem and as if by a miracle, the algal problem will more than likely go away.  The number one thing to do if algae start to take over is to test your phosphate levels.  The goal is to keep the levels low enough to keep your plants happy.

How much phosphate is too much?  In nature it is often less than 0.01ppm.  The bottom line is if you can detect it with a standard aquarium test kit, there is more than your plants need.  However, the official line is something along the lines of:

0.01 - 0.03 mg/L - the level in uncontaminated lakes

0.025 - 0.1 mg/L - level at which plant growth is stimulated

0.1 mg/L - maximum acceptable to avoid accelerated eutrophication (and arguably the point at which things start going berzerk in aquaria)

> 0.1 mg/L - accelerated growth and consequent problems

Tap water is often already too high in phosphates (mine is) so water changes may well not solve the problem.  I contacted my local water provider to find out the average phosphate levels which weren't published.  They seemed delighted I asked and were only too happy to tell me!    The solution? Personally I use a phosphate adsorber in my external filter canister.  Easy peasy and doesn't add anything to my tank water.   Adding chemicals to your tank water is almost never a good move and usually only good for the people who sell the stuff.

How do I know all this?  Partly it's because I am a biologist and have done my research.  Also it's a case of "been there, done that" in my aquarium which I've been running for 25 years.  I now regard algae as a useful indicator of my tank chemistry, not as a problem.

Guy's name is Omega - so thank you to Omega, if you should happen to read this... 


Anyways, this sounded like a potential candidate for what's happening to my poor old Hygrophila Costata stem plants and consequently I ordered myself an API Phosphate test kit...  My readings are 2ppm, possibly a little tad higher (jumps from 2 to 5 on the colour chart - mine looks like a definite 2 but guess it could easily be 2 point odd...?)... 

Yikes Cookie lad, get your panic on dude...!!!   

Some Seachem Phosguard has just been ordered and I shall try a small amount in the little surface skimmer, see how that goes for a little while...  If the results are too slow, I'll add a proper layer in the cannister filter... 

Just wondering if any of you ladies & gents have much experience with dealing with phosphates...?

For sure...  I'll post what happens up on here...  Those Hygrophila Costata have been getting to me and as you know, I was gonna rip them out - hence the search for replacements...  But that's not really addressing the root (excuse the pun, lol) cause, and with a bit of luck, sorting the phosphates could well be and the H.Costata can come back to full health... 

I don't "see" any algae problems on the whole and have a great clean up crew of 12 Amano shrimp, 1 Lemon BN Pleco & then Rabbits snails plus Faunus snails...  Between them, they do a superb job on the whole...  Tank lights also on a timer etc...

It is definitely for the sake of the plants, with the H.Costata in particular, that I am having a go at this phosphate malarkey...  They used to grow so well and have a potentially very nutritious environment etc...  The part of Omega's article that touches on what is happening with the H.Costata is where he says: 

"Phosphate is naturally present in extremely low amounts in healthy watercourses and plants have consequently become superb scavengers of phosphate.  Add phosphate and plants will at first greedily take it up and grow faster.  But in the fish tank, the levels tend to insidiously rise way beyond the needs of the plants, unless you have no/very few fish or do sufficient water changes with phosphate free water.  Even worse, and apparently much less well known, excess phosphate will eventually stop your plants growing because it interferes with iron uptake.  Your plants will gradually go yellow, especially the new leaves.  At this point, some people looking at the symptoms will suspect a deficiency and perhaps fertilise the tank.  Increasing available iron might help a little but ultimately, it's futile.    Growth will slow and eventually leaves will start dying.  Even more nutrients will be released into the water as they do so."

That appears to hit a bull's eye for what is happening in my tank, and then to discover my phosphate levels are a touch too high at 2ppm, this has got to be worth a closer look at...  I'm not expecting miracles of course - there is no magic wand for any part of our chosen hobby - but will be delighted if addressing the phosphate level does improve matters for the plants... 

I actually use Poly Filter in the surface skimmer, as it happens...    Marvelous stuff, for sure...!!!

My phosphate readings this morning are the day after a PWC, funnily enough... 

One thing that could be contributing to elevated phosphate levels though, I do think there's a chance that there is a small degree of over feeding...  Certainly not by much, but as little as I do feed, all the fish do look suitably healthy and are clearly not starving...  The Corys look a tad plump even, little blighters...!!!  In their case though, I think they get considerably extra food in terms of micro-critters...

I have been using phosphate in my aquarium for about 6 months. I started using a small dose after reading an article on Ferts. The article implied that the amount of Phosphate in the tank should be approximately 10% of total nitrate in ppm. I know that our local water company adds phosphate at a dose of 1 ppm to prevent the leaching of heavy metals from pipes into the tap water. So I gauged how much I would need to add to bring it up to 2 ppm. Nitrate is 20 ppm from my 50/50 tap/ RO mix.
I haven’t really seen a significant difference in either plant growth or algae reduction.

I don't think much of that article. Plants need a lot of things but they only need them in trace amounts. Any more is an excess. And if I remember correctly (and my experience has reflected this) proteins contain phosphorus and nitrogen in a ratio that produces, after metabolism, waste phosphates and nitrates in the ratio of 1:10 anyway, so they ARE a tenth of the nitrates in your average tank, which is excessive for plants...

I don't believe they need to be added to a tank with fish at all, rather removed. Only the other trace minerals that plants require need to be added, so that everything is in correct proportion.

I have experience with combatting excessive phosphate, in the days when I was trying to get my planted tank established. The solution to my problem wasn't to reduce the amount of phosphate in my tank. The following is quite an in depth explanation. This is because I had to do a lot of research (and experimentation) to find the solution. Hopefully, if I can share some of what I found, it'll save time and effort for others. (I am not a biologist, but I am a scientist and can mostly get my head around the chemistry).

All plants, aquatic and terrestrial require 3 macro nutrients: N, K and P in the correct ratios. N is nitrogen, K is potassium and P is phosphate. Plant growth is usually limited by the nutrient/s (micro or macro) that is in least supply. It is also worth bearing in mind that in this context, light and carbon are also considered nutrients.

Phosphate is in fish food (or as a product of metabolism as @Hampalong says, I can't remember which) in quantities greater than that required by the 'golden' ratio. Therefore fishtanks rarely have issues due to lack of phosphate: overfeeding and phosphate are usually the number one reason for algae problems. But they are not the only reason.

My tap water has particularly low nitrate levels (<5ppm), so without supplementing nitrate, I can't get anywhere near the right ratio of phosphate: nitrogen.

Estimative index fertilising is a method that intends to overdose all nutrients, including the one in lowest required quantities. But it also relies on frequent, large water changes to remove the excess of all the other nutrients before they cause other algae issues.

By looking at the type of algae that is a problem, you can identify which nutrient you have excess of and by looking a plant issues, you can start to identify which nutrients are the limiting factors of growth.

I have found this website really useful as it looks at both. (On different pages)
http://www.theplantedtank.co.uk/algae.htm

I hope this helps explain a bit about aquatic plant nutrients and helps you identify the issues particular to your tank.

It appears there are two schools of thought here. 1) :- Remove phosphate to eliminate algae growth or 2 :- Balance Nitrate and Phosphate levels to eliminate algae growth.
Based on what I’ve read I would imagine that case 2 only applies in hi-tech planted aquaria using EI dosing and frequent water changes (50% per week) to keep the nutrient levels in check.
Does anyone else share this view ? Or have I over simplified this ?
I am going to stop dosing my tank with phosphate at any rate. I now think it’s a bad idea.

Essentially low tech here too, or what you might call "hybrid" perhaps...?  Substrate set up as Walstad Method for the majority of the tank and quite a few plants really...  More being added as an ongoing thing too...  Basically, I aimed for a tank that would require less work and maintenance when compared with a high tech set up - this is essentially why I will most likely never go down the EI ferts route... 

My aim with the phosphate levels is not to remove them completely per se...  but to get them down to a potentially less problematic level... 

Omega, a biologist and an aquarist of 25 years experience, states these levels in his/her posting: 

0.01 - 0.03 mg/L - the level in uncontaminated lakes

0.025 - 0.1 mg/L - level at which plant growth is stimulated

0.1 mg/L - maximum acceptable to avoid accelerated eutrophication (and arguably the point at which things start going berzerk in aquaria)

> 0.1 mg/L - accelerated growth and consequent problems

Judging by this table, I think the 2ppm (the equivalent of 2.0 mg/L unless I'm mistaken...?) that I have in my tank is considerably too high and by quite a significant margin at that...

Quoted from Diana Walstad book: 

... The phosphate concentration in unpolluted natural waters is indeed very low, between 0.003 and 0.02 mg/l P.  This limits algal growth, since only a few algal species can use less than 0.02 mg/l P. 
However, home aquariums typically have much higher phosphate levels.  My own aquariums contain about 1-5 mg/l P, which is more than sufficient for almost any algal species.  Because of the continuous addition of phosphate via fish food, it is highly unlikely that phosphate deficiency would ever limit algal growth in the typical aquarium"

 

Then in one of the Q&A panels that feature heavily in the book, a guys asks about algae and his set up is very high tech...  He states his phosphate level as being 0.15 mg/l...  Diana, in answering him, comments: 

"Although your phosphate levels are indeed very low (lower than for most aquariums), they are quite sufficient for many algae.  As you have seen, trying to reduce P levels in the aquarium to levels that will eliminate algal growth is almost impossible."

The question, or questions, around the whole phosphate business are intriguing to say the least, and absolute clarity on the subject is elusive...  But anyways, if anybody is following this thread, then you may find these excerpts from Diana Walstad's "Ecology of the Planted Aquarium" interesting and informative...

As for me, I still haven't got a Scooby...!!!   

The Seachem PhosGuard did arrive this morning and a layer added to my surface skimmer filter...  Will be interesting to see if this does make any measurable difference or not, and I will certainly report back here whichever way it goes... 

20ppm, if that...  With all the plants in there, water parameters have never even once been an issue - to the point that I find it bizarre that so many new fishkeepers struggle with cycling...  I was really lucky I think, and had no issues at all...

Recent pic of tank: 



That is before the Bucephalandra were all added, although they're too slow growing to have any real impact of course...  Got a bunch of additional plants in a quarantine tub as we speak, so the plantings are continuing...  I may yet also replace the sorry looking H.Costata stems at the back/middle as they really are looking unhappy and of course this is what fired me up on the whole phosphate thing...  The fish seem to love those tall stems though, which is why I really hope that a phosphate reduction - if it is even possible at all - may help...?

Having said all that Helen, and after reading as much as I can about this curious subject, I'm starting to think that the likelihood of seeing a phosphate reduction is very low...  There are just too many sources of phosphate, especially as my tap water level is high...  It's gonna be like fighting a never ending losing battle, I suspect...