# Nitrate/Phosphate Availability?



## trag (Jan 9, 2008)

Is there some reason that nitrate/phosphate tests would show them present in my water in sufficient concentration and yet they would somehow be unavailable to the plants?

I've posted a few times about the problems I'm having with my banana plants and water wisteria. I have finally started to observe them closely and frequently, and the form of the leaf loss indicates nitrogen deficiency (or possibly phosphate). The leaves turn brown near the edges and start to dissolve inward. The banana plant leaves are especially prone to dissolving where the stem meets the leaf, rendering the leaves useless. The WW can't grow leaves fast enough to make anything more than tiny little leaves less than 1" long.

However, my phosphates test rather high. Apparently our tap water is fairly rich in phosphates. It's hard to definitively interpret the color, but it looks like between 2 and 6 PPM of phospates. 

The nitrates vary. The time I tested just before a water (~50% every two weeks) change the nitrates seemed to be about 50 ppm. However, just before the next water change, the LFS tested my water and the reading was under 20 ppm. I have the API test kits at home and the LFS uses the Tetra. The 30 gallon tank in question is full of swordtails -- like 70 - 100 of them.

So, I guess my nitrates could be too low after water changes and too low until just before the water changes, but it seems hard to believe given the fish population in the tank. 

My tests seem to indicate that I have enough phosphorous and nitrogen, but the plants seem to be saying otherwise.

I'm additionally puzzled by this because I put some pond plant tabs in the substrate, but perhaps they only supply rooted plants and don't enter the water column very well?

The tank also contains a large population of java fern which is thriving just fine. Perhaps it is an aggressive nitrogen or phosphate sequesterer?

I'll probably just get the appropriate dry fertilizers from Planted Aquarium Fertilizer, but this seems odd. I had been dosing only CSM+B, Iron and K2SO4 up to this point. The tests seem to indicate that I don't need to supplement N nor P, but the leaf symptoms seem to indicate otherwise.

Any thoughts or speculation?


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## ray-the-pilot (May 14, 2008)

I can grow anything in my aquarium and I have the same problems with Banana plants. For some reason, these plants are especially tasty to fish. My angels chew in from the edges and my pleco’s eat in from the middle. Ultimately they eat the whole thing banana tubers and all. If you keep them growing at full speed, you can get ahead of the foraging fish but it is not that easy. I suggest upping your CO2 to as high as your fish can take and increasing your light to as high as you can without too much algae. 

If you do not have fish predation, these plants are easy to propagate. Just tare off a leaf and let it float arround your tank. Eventually it will form a root system and a whole new plant.


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## trag (Jan 9, 2008)

ray-the-pilot said:


> I can grow anything in my aquarium and I have the same problems with Banana plants. For some reason, these plants are especially tasty to fish. My angels chew in from the edges and my pleco's eat in from the middle. Ultimately they eat the whole thing banana tubers and all. If you keep them growing at full speed, you can get ahead of the foraging fish but it is not that easy. I suggest upping your CO2 to as high as your fish can take and increasing your light to as high as you can without too much algae.
> 
> If you do not have fish predation, these plants are easy to propagate. Just tare off a leaf and let it float arround your tank. Eventually it will form a root system and a whole new plant.


Thank you. I guess the swordtails could be munching on the banana plant leaves. There are also three otocinclus in there, which could. But does water wisteria (Hygrophila difformis) have the same tasty quotient?

Regarding banana plants being easy to propagate, that's part of what makes this frustrating. WW and banana plant should be easy to grow, and they were doing fine for a couple of months. Sigh.

I'd be happy to give up on banana plants (or move them to the guppy tank) if the darned water wisteria would grow.

I tested my water again last night. GH = 8 or 9 (added two drops there). KH = 8. Phosphate = 10ppm. Nitrates = 20 - 40 ppm. pH = 7.6 (added a little Sea Chem Acid Buffer to try to bring it down.) No detectable iron or maybe just a smidge of purple color in the test. I'm about four days overdue for a water change. Busy weekend.

Notes on pH. A few weeks ago, but long after my wisteria and banana plants collapsed (they grew fine for 2 or 3 months) my pH was 6.0 and my GH was about 5 and my KH was about 3. So on the recommendation of the LFS, I added Sea Chem's Alkaline Buffer. I used as directed, but one application took my pH up close to 8. I have since purchased the Acid buffer, but I've only used it once so far. It seems to have brought pH down to 7.6 so I have a few more applications to go. Now, I'm wondering if the stuff in Alkaline Buffer which contributes to GH is balanced with respect to calcium and magnesium. Anyone know?

Notes on Iron. I've read that the test kits aren't terribly reliable. I'm using the Seachem "Iron Multi Test Kit". I've been dosing CSM+B, Chelated Iron and ferrous gluconate at levels that target .5ppm for *each* of those three chemicals. But I haven't tested my water right after adding them. I never remember until several days later, at which point the iron seems to be close to zero. So I guess there could be a huge sink for iron in my tank, either the java fern or the natural gravel.

Notes on Chronology: The two or three months when the plants were growing great I was not dosing with anything. When they started showing problems, I tried adding some stuff I had on hand, which included a five+ year-old SeaChem product which said it added iron and micronutrients, some old Hawaiian Marine trace elements (really intended for marine applications, but okay in freshwater in limited amounts), and some PlantTabs with Iron.

Then about two months ago I tried adding the pond plant tabs which purport to include micronutrients as well as macros. Those may be contributing to my high phospate reading.

None of those solved the problem, so I trotted out my test kits and got my water tested at the LFS as well. Added the Seachem Alkaline Buffer about a month ago to bring my GH, KH and pH up. And bought the CSM+B, Potassium, and iron supplements from Aquarium Fertilizer and started using them about two or three weeks ago.

But even since starting the more measured fertilizer approach, I've seen new leaves start out promisingly and then whither.

That does seem to support the fish predation theory. I'm not sure it applies to the water wisteria though. I tried moving some sprigs of WW to the other 30 gallon tank, with no swordtails, just guppies and it did not flourish there either. I'm beginning to wonder if there is some way in which java fern is inimical to WW.


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## wet (Nov 24, 2008)

I like how you're thinking of this and describe your tank. But there's a couple important things I think you should consider then let us know what you think:

1) The biggest nutrient for plants is Carbon, and the easiest way to add this is CO2, but you ignore this part of ray-the-pilot's post. If you experience stunting of any fast grower, you should think about macros first, and by extension, C.

2) You should stop using pH buffers because this is stressful to fish and less important to (most) plants. Remember stability is more important than a number.

3) When you see symptoms in your plants and suspect a nutrient limitation, like you've suggested with P here, and the only thing stopping you is a test or some number, dose it anyway. Go slow and take your time and watch the plants (with something like Wisteria you should see a difference in a week or so). If they do perk up, keep adding P and don't stop until the Wisteria stops improving. Then see how much KH2PO4 you're dosing when you get there: this is the number you care about.

(I think your problem is probably CO2 because if I'm gambling I'm going with the thing that's ~40% of plant mass. But I think you're right about likely PO4 limitation, especially if your plants were growing well before. But, unless this is designed to be a Natural or lower uptake tank, you should always think about and check CO2 first.)

A little tangent: sometimes, when folks say "Throw out your test kit," I think it turns off gardeneres because they interpret this to suggest EI does crazy math things or implies it is so perfect it doesn't need a test. I've always thought of the saying as something entirely different: that plant and fauna health is the only test that matters. 

In regards to why the PO4 test measures as it does, you should try to measure a known dose of PO4 into known clean (DI or RO, not tap) water, then see what the test says. Folks can help with this or you can use many online calculators (say, using a 1 gallon or 0.5L or whatever container as your tank volume). One other reason folks suggest not using kits is that often times it is cheaper to buy a scale, a couple containers with volume markings, and be much more accurate while still having cash left over for other hobby stuff.


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## trag (Jan 9, 2008)

Thank you for the advice. I appreciate the help and the chance to chat about this. Specific comments below.



wet said:


> 2) You should stop using pH buffers because this is stressful to fish and less important to (most) plants. Remember stability is more important than a number.


Until I started having this problem I didn't worry about it. Although 6.0 pH does seem a little low. Still, the fish didn't seem to mind. On the subject of stability, though, water changes are likely to bump that low pH up suddenly. Something buffered closer to the tap water (almost exactly 7.0) would probably be more stable. Is there any harm in pH buffers once one has hit a stable mark, assuming one can maintain it?



wet said:


> 3) When you see symptoms in your plants and suspect a nutrient limitation, like you've suggested with P here, and the only thing stopping you is a test or some number, dose it anyway.


Okay. That sounds like a plan. Thank you.



wet said:


> (I think your problem is probably CO2 because if I'm gambling I'm going with the thing that's ~40% of plant mass. But I think you're right about likely PO4 limitation, especially if your plants were growing well before. But, unless this is designed to be a Natural or lower uptake tank, you should always think about and check CO2 first.)


Yes, it is a natural (or at least non-CO2 supplemented) tank and the plants did grow great for two or three months. I suppose they could have been using up some kind of carbonate reservoir. I've looked at the info on CO2 and I'm considering it, but I'd really rather not. I don't need my plants to grow faster than anything, I just want them to stop dieing at this point. The light on the 30 gallon in question is a pair of 30 watt T8 bulbs. They're on about 10 hours a day with a 4 hour break in the middle. Hmmm. That adds up to 14 and I think the interval is actually 13; first on at 7:30AM, Last off at 8:30PM.



wet said:


> A little tangent: sometimes, when folks say "Throw out your test kit," I think it turns off gardeneres because they interpret this to suggest EI does crazy math things or implies it is so perfect it doesn't need a test. I've always thought of the saying as something entirely different: that plant and fauna health is the only test that matters.


I'm all for throwing out the test kits. I wouldn't have turned to them at all, but when my first few efforts didn't solve the problem, I decided I needed more information. However, I'm not sure the test kit info is really helping.  At least I know that my ammonia and nitrites are undetectable. Of course, my fish are alive and healthy, so I already knew that. Which tracks pretty well with your point.



wet said:


> In regards to why the PO4 test measures as it does, you should try to measure a known dose of PO4 into known clean (DI or RO, not tap) water, then see what the test says. Folks can help with this or you can use many online calculators (say, using a 1 gallon or 0.5L or whatever container as your tank volume). One other reason folks suggest not using kits is that often times it is cheaper to buy a scale, a couple containers with volume markings, and be much more accurate while still having cash left over for other hobby stuff.


I've seen directions for this. I think that's a good idea to calibrate my PO4 test, and my nitrate test as well. My iron kit comes with a little bottle of sample iron solution for just such a calibration, so I'll do that too. It will be interesting if nothing else.

However, I don't have any PO4 compound on hand. So I guess it's time to order some. That will let me follow your advice above as well. I already have KNO3 on hand (for making rocket engines...).

In the meantime... I move two of my three banana plants as an experiment. I'm not sure it was a good idea, as they had nicely developed root systems, but I didn't know that until I dug them out.

I put one of them in the other thirty gallon tank. It's just like the tank under discussion, except it has no substrate, and it has a pair of T5HO 39watt lights instead of the older 30watt lights. It's on the same timer. Also has a large population of java fern and has guppies instead of swordtails. I have been having trouble with the java moss in this tank. Similar to the problems with the WW and BP in the first tank. Since I've been dosing K and CSM+B and Iron the java moss has started making a come back. I potted this banana plant in a small red clay pot. I put large gravel (~1/2") in the bottom to block the holes, then potting soil with one pond plant tab (20 - 5 - 10 + micros) Pond Plant Tab, Scroll to bottom and fine gravel on top to hold the soil.

I put the second banana plant in my 5 gallon maternity tank which has java moss and some kind of whorly plant that came with the cherry shrimp. It has a single 15 watt 6500K CFL light. The banana plant is just floating unrooted in that tank.

It will be interesting to compare the three to see if there are any changes.


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## wet (Nov 24, 2008)

> On the subject of stability, though, water changes are likely to bump that low pH up suddenly. Something buffered closer to the tap water (almost exactly 7.0) would probably be more stable.


This is true. But anecdotal evidence (the bagillion people over a bagillion years who use peat, acidic substrate, driftwood, CO2...) says it's not actually pH that matters for our fish -- within reason -- but changes in KH. Now, some change in KH isn't terrible: KH will raise naturally as water evaporates, for example. I suspect your pH drop is actually due to one of the sources there or perhaps organics in general, but that with regular water changes the change in KH is not major. (This is the same principle as, say, EI with a given water change schedule only approaching some number.) The impact of those water changes, using the same sample of folks before, isn't a huge deal. 


> Is there any harm in pH buffers once one has hit a stable mark, assuming one can maintain it?


I don't think so, provided we do the gradual thing. It's much like someone using limestone or gradually increasing their ratio of RO water to change a tank to hard or soft water, respectively. But notice how those buffers gradually adjust KH (and by extension pH) in a way you can't get from a bottle.

I think the rest of your plan is good and the experiment educational (it's always good to see how some plant reacts in a variety of conditions), though on your T5HO tank you should be thinking again about macros and maybe starting with small doses of KNO3 and watching the plants. If you're not aware, KH2PO4 is also available at many drugstores as Fleet Enema, and I am sure someone has posted instructions somewhere on APC. With this nutrient you should be set since you've already covered K, micros, and rocket sauce.

It's good you're currently dosing what you're not getting from food. Worth stating that both Walstad and Barr/Plantbrain also feed a lot. An alternative thing to try while you wait for your fertilizers.

(Fertilizers are much "cleaner" than fish food. Again, think organics.)


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## Diana K (Dec 20, 2007)

I also would quit worrying about the pH. Get the GH and KH right and let the pH do whatever it wants. Swordtails and Guppies are hard water fish. I would get the GH and KH up over 5 degrees for sure, and approaching 10 degrees would be better. (Unless you are keeping plants that absolutely demand soft water, then separate those plants into a soft water tank). Most plants will do just fine in harder water. 
I use baking soda for KH and Barr's GH Booster or Seachem Equilibrium for GH. Either of these are balanced Ca & Mg sources. 

You say the phosphates seem high, well, some pH adjusters include phosphates. Quit using them, unless you specifically want more phosphates. Seems you have an OK ratio between N and P, though. 

* Calibrate all your tests. 
* Add carbon. In a 30 gallon tank you could do this as easily as (2) 2-liter DIY/Yeast bottles. Alternate recharging them. Or Excel. Or try (as you are doing) keeping some plants right up at the surface, with a leaf or two exposed in the air. If that plant starts thriving then you know part of the solution is carbon. That plant is getting its CO2 from the air. 
You have enough light that the plants will need some added carbon. 

Your tanks are heavily stocked. Nevertheless, your plants ought to keep the N and P from fish food under control, even feeding as much as is needed by that many fish. 
There is something else lacking that is slowing the plants down. N and P are not locked up in a way the plants cannot use them. Something else is missing, and without the complete supply the plants cannot use even things that are available in luxury amounts. 

When I had similar problems (overstocked tanks, high NO3) the problem was low light (1 wpg) and lack of K (holes in the leaves), Fe and C. 
I doubled the light, added Excel, and added K and Fe. This was a good solution for my situation. By adding what the tank lacked the plants were able to increase their intake of N so the levels were better for the fish, and I could do fewer water changes. 

In your case I see you seem to be addressing most items from an approach that seems 'old school'. pH and Phosphates are not the enemy. Keeping these 'under control' should not be the main approach to tank maintenance. 

'old school' here, means that in the early days of aquarium keeping there were not so many tests available as there are now. Fishkeepers had to make do with pH tests, and had no idea what the minerals were doing in the water. Since the mineral levels are somewhat related to the pH they tried really hard to control the pH not realizing they were really monkeying with the minerals in their attempts to keep the pH at a certain level. All the information from these times is directed at keeping the pH stable, because that was the only way they had of even trying to keep the GH and KH stable. These are not the same as pH, though, so their attempts at controlling pH sometimes worked (fish thrived even if the pH did wander a bit) and sometimes did not (fish died even if the pH was under control). 

The phosphate issue came about when detergents had phosphates and water treatment for waste water was minimal. Phosphates built up in streams and lakes and resulted in a lot of algae growth. Then the algae died, decomposition removed the oxygen from the water, and the fish died. This really got peoples' attention. There were other wastes adding other nutrients to the water, too, so phosphates were not the only thing changing in the water and encouraging the algae. They got the blame, though. So now the aquarium trade has its share of products that are labeled "No Phosphates!" and phosphate removing products for the filter as if this is a problem. Plants and all life need phosphorus. It is not a problem to have phosphorus in the water. Lack of it can cause problems for plants.


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## trag (Jan 9, 2008)

Diane and Wet, thank you for the additional comments/suggestions. I am experimenting and will report back if there are any results of note.


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## trag (Jan 9, 2008)

So, two weeks later...

I've gone to a full EI regime of fertilization. I wasn't adding nitrates and phosphates before because they test fairly high in my tanks already. However, I wasn't being all that regular about adding the potassium and iron and CSM either.

So, I"ve been adding everything regularly, plus a little dolomite solution and calcium sulfate as well.

The banana plant in the original tank is much improved. I don't know which nutrient it was missing, but I think it must have been missing something. It now has four large (but not extra-large) leaves, none of which are dissolving or rotting. 

The banana plant which I potted and moved to the lower 30 gallon tank (bare tank, no substrate, hence the pot, and T5HO instead of T8 ) is doing great. It has four extra-large leaves. I also stuck a sprig of water wisteria in the edge of the pot, and it is growing new leaves. I wouldn't call it fully recovered, but that sprig is putting on new growth and boot-strapping itself up back to full size. 

The banana plant I floated in my maternity tank is not growing very fast and it's "bananas" are disintegrating. I suspect that banana plants really like to be rooted in a substrate. 

So, I think the banana plant problem was some kind of nutrient deficiency. It would be nice to know which one or ones, but that would take a lot more experimenting. For example, I may stop dosing phosphate for a couple of weeks and see if the improvement continues or stops. Then stop dosing nitrates and observe. Etc.

The Water Wisteria is another story. As I mentioned, the sprig I moved to the bottom tank is improved. I have been carefully observing a large stem (from the good growth period) with three small sprigs of growth for a couple of weeks. I think, but am not certain, that something is eating the new growth. I could have sworn that I saw two new leaves emerging and about to spread out and the next day they were back to little green nubs. I'm not 100% certain yet, but I will continue observing.

Would Otocinclus eat water wisteria sprouts? The tank has swordtails, cory. aeneus, and three otocinclus. I would not have thought that just three otocinclus could devastate a dozen or so stems of wisteria, but they've got all afternoon to browse... 

Of course it could be the swordtails or corys, but I think the wisteria problems did not start until a week or so after I added the otos. Any similar experiences out there with otos?


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## wet (Nov 24, 2008)

Not had anything even remotely similar to that with Otos, but have had Swordtails munch of Synonganthus 'Belem' in the past, fwiw. Since you've shown the benefits of fertilization both in the water column and soil in separate tests, have you thought about potting the H. difformis is a non-swordtail tank as a sanity test?

I'd suggest you keep doing what you're doing before limiting nutrients again, fwiw. Easier for plants to recover from our experiments/questions/mistakes when they have plenty of nutrients as reserves. Best not to mess with a tank just getting its balance.


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## trag (Jan 9, 2008)

wet said:


> Not had anything even remotely similar to that with Otos, but have had Swordtails munch of Synonganthus 'Belem' in the past, fwiw.


Yes. I posted the specific question about the otos over in the "Fish for the Planted Aquarium" forum, and the consensus there also seemed to be that it's probably the swordtails and not the otos.

I really wanted wisteria in that tank. It's frustrating when the fish don't cooperate. I wonder if they would eat Hygrophila polysperma too.

I have plans to set up my 90 gallon tank and move the swordtails colony there, but if that means I can't have wisteria in the tank... Sigh.



> Since you've shown the benefits of fertilization both in the water column and soil in separate tests, have you thought about potting the H. difformis is a non-swordtail tank as a sanity test?


I did put a little sprig of it in the pot with the potted banana plant. That pot is in a different non-swordtail tank. Specifically, it is in a guppy tank.

I have two 30 gallon tanks on a wrought iron stand. The upper tank is the one I started the thread about. The lower tank is a guppy tank sans substrate and with T5HO lighting instead of T8.

The sprig in the pot is growing well. It has produced two new 1.5" leaves with ... what's it called when the leaf shape has lots of points instead of being just round... that shape. In the same time the sprigs I'm observing in the upper, original, 30 gallon tank have produced some bright green little nubs which might have almost been leaves if they hadn't been nipped away.

I'm thinking about moving that stem-with-sprigs from the swordtail tank down to the guppy tank as well. If it suddenly starts growing, then it's almost certainly fish predation, although I suppose it could also be T5HO vs. T8 lighting or potted vs in-substrate, but since everyone says wisteria does okay in lowish light that seems far fetched.



> I'd suggest you keep doing what you're doing before limiting nutrients again, fwiw. Easier for plants to recover from our experiments/questions/mistakes when they have plenty of nutrients as reserves. Best not to mess with a tank just getting its balance.


Yes, there is that. Thank you for all the help and advice. I appreciate it.

BTW, my java moss in the guppy tank had pretty much completely died off and since I started dosing fertilizer it has recovered too.

Since the java fern was still doing fine (or well enough) in both tanks this seems to imply that java fern has some way of coping with deficiencies (or causing deficiencies) that most other plants have trouble with.


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