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Old 08-11-2004, 08:05 PM   #1 (permalink)
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Default My zero NO3, PO4 tank with plenum

Hi all,
I got bit hard by the plant bug about a year ago after not having an aquarium since I was a kid. Even after trying several different methods, I could never quite win the battle with algae. I decided to make up my own method. I have tested my water and it has the following specs:
TDS: 35ppm
KH: 30ppm
pH: 6.1
CO2: 35-40ppm
PO4: 0ppm
NO3: 0ppm

So, clearly the plants have to get their nutrients from the substrate. I was reluctant to use soil because my feeling is that dissolved organics (DOP and DON) are algae's nutrient source. Instead, I am using a "nutrient plenum" which I read about in the archives on to provide trace elements and positive cations.

I basically set up a 0.5" thick cavity under a substrate of flourite+profile. The plenum has two thin tubes feeding it. I inject Flourish into the plenum and it is allowed to diffuse slowly through the substrate. To prevent diffusion into the water column, heavy ground cover is good. Of course, until the ground cover is established, injecting nutrients should be done judiciously (i.e., not put too much in). I initially put a foam layer between the gravel and the plenum, but I found that very little was diffusing from the plenum into the substrate.

For macros, I am using quite a few Jobes plant sticks buried under the plants. I have not had any trouble with leaching into the water column.
I will try to post some pics, but I can't seem to get them to show up at the moment. Let me know what y'all think.
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Old 08-11-2004, 10:05 PM   #2 (permalink)
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What types of test kits are you using.
Have you run them against known standards?

Algae is not limited via the water column. The waste from the fish and plant decay alone will solve that.
A Plenum is a waste of space IMO.
There is flux out of the substrate also, it's occuring.

I think you will find over time and after a few plantings, you might not like the jobes. But adding PO4/NO3 is not an issue as far as algae is concerned. If you had algae issues in the past, it was not from having those present, it's generally from not enough NO3/PO4/CO2.

Tom Barr
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Old 08-11-2004, 10:38 PM   #3 (permalink)
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I know that some phosphate and NH4/NO3 will come from fish waste and feeding. However, I do about a 40% water change everyday (my tank is small so this is very easy). Plus, my fish population is not that large -7 tetras and one small SAE. I feel fairly confident that my PO4 and Nitrate levels are close to zero.

Regarding the plenum, it's not really a plenum that's used typically in reefs. I mean, that it's not meant for denitrification. It's just a means to dose nutrients through the substrate first. My fluorite is pretty much covered with plants like the glosso, so not much escapes throught the water column. I have tested with a TDS meter before and after dosing to verify this.

Anyhow, I don't think denitrification is that bad, because deep substrate denitrification means ammonia which plants prefer and it is isolated from algae in the water column.

Oh, sorry about the photo I will resize the next ones I put up. Is there a way to edit previous postings?
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Old 08-12-2004, 07:53 AM   #4 (permalink)
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Well with 40% daily changes I think you will probably never test much in the water regardless of how much is coming out of the substrate. I think that may be the key to this tank, if you wait a week between water changes I'm sure test results would be different and problems tied to the extra rich substrate may occur. Plus, by changing water so often I think you are somewhat simulating what occurs in nature, that is constantly flowing water that is poor in nutrients however never depleted because of the constant flow of new water. We use higher levels because the water is the same for a week and we don't want it to become depleted, if you change it daily the nutrient levels required are probably barely readable by most of our test kits.

Wish I had the will power to do daily water changes

Giancarlo Podio
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Old 08-12-2004, 01:59 PM   #5 (permalink)
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Well, the point with the daily water changes is the fact that plants can grow with an extra lean water column. My goal was to basically make it impossible for algae to grow. Also, my substrate is not rich, except for the Jobes sticks.

I think if l left it for a week, there would not be significant leakage from the substrate. I do the water changes to remove organics produced by the fish and the feeding, and maybe the plants. I can tell there are organics being produced because of the surface scum. Surface scum is not present when the water is really clean.

When I progress to a larger tank, obviously the 40% water changes will not be possible. In that case, I will probably have to employ chemical means to keep the water pure, i.e., a lot of activated carbon, ozone, and/or a protein skimmer. I like gadgets so the more the better .

Is it possible for the moderator to delete my 2nd post, because the picture is too large and it makes it hard to read. The image hosting website that I put it on does not allow for easy deletion. Thanks.
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Old 08-12-2004, 02:31 PM   #6 (permalink)
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Thats pretty good looking Rotala macranda green (Right???). Its a cool idea. I want to try something like that out on my 20 gallon. But i think plantbrains advice is real good. A lot of people follow it and get good results.
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Old 08-12-2004, 05:04 PM   #7 (permalink)
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The plants on the picture look very healthy (with the exception of the unusual white spots on the Lobelia). Clearly you are doing something right.

Yes, Tom's advice is used by many, but there are other good ways to run a tank and your tank is another proof for that. To me the "best" way to run a tank is the one that requires less work. Your daily water changes would be a burden if you try them in a bigger tank.

But I think that what you have done makes a good point about the importance of water purity.

May be I missed it somehow but did you have any algae problems at any point of the development of that plenum tank or not?

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Old 08-12-2004, 08:33 PM   #8 (permalink)
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40% daily water change with what kind or water?Tap or RO or?

Most tap has some NO3, some has PO4 like my old tap water here in Marin.

The dutch did large frequent water changes and had high NO3/PO4 in their tap. Many places have this.

The issue for me is the moss, it does not have roots. So it's getting enough nutrients.

And if it's able to grow, so is algae.

I've found algae in places where we could not measure any NO3 or PO4.
I just do not buy folks saying algae can be limited while the plants are not.
I've never found evidence of this in the research either and I have looked.

Algae phyisology just does not work that way.
Plants will grow in those same places also, but the substrate is the source.

Many waters have a pH of 5 and no measurable hardness/nutrient levels.

The other issue is that the nutrients are often used up as fast as they leech so you really do NOT know how much of the jobes is going into the water column or is available for either plant of algae.

Plants also leak a fairly substantial amount of nutrients.

Both Tropica and Amano have done small tanks like this with no substrate and water column dosing and daily changes.

If you are going to go to the effort of a daily water change, dosing is not hassle.

As far as elements causing algae, this is fairly clear.

But I will challenge you to show evidence that you can limit algae by nutrient limitation to the water column and still have healthy plant growth.

I can clearly grow plants with zero algae with high nutrients, so does the nutrient levels in the water help?


You seem to assume that they do.
That was my point.

We can find many examples I nature of this situation, but it does mean it's preferred by the plants nor limits algae in any way.

That is a dangerous assumption.

Plants have a source of nutrients, whether from the substrate or the water column, they will do well.

You will get higher growth rates, thus preference with the water column.

It's not an issue of MY method vs a substrate method, that has nothing to do with it. I'm making a point you gain nothing by doing such a method dealing with algae.

If you dosed back the KNO3/KH2PO4 and did daily water changes etc, the plants would grow great also without any substrate and there'd be no algae. I've done that also for close to 10 years. I also tried the rich substrate approach, we have archives and archives of this on the APD, we went around and around with it there.

This is nothing new.
Not sure why people think it is, sort of ironic.

I did that substrate water column clean method also.
One thing that helps the water column clean method today is huge water changes and higher CO2 than in the past.

This seems to have a negative effect on the algae spores(water changes) relative to the larger plants which can take the shock better.

It's not so much the method, it's the large water changes daily.
Using TDS is not necessarily going to tell you your NO3 level at all.

If you are using CO2 and have that measurement, then you must have a KH and therefore some TDS, likewise for GH to some degree.

Try adding a small amount of a stock solution of KNO3 to see.

The small trace amounts of PO4/NO3 in the tap water are not going to show up. Unless you are using reconsituted RO etc and have measured the tap with a good quality NO3 kits, it could very well be the case.

Folks use to say I had "magic tap water".
There's no magic and because I am being critical and looking into this question it does not mean I am being anything more than that.

These are valid issues that sometimes cannot be addressed directly so finding other ways to solve the problem or question is sometimes needed.

I'm not partial to a method, I'm partial to an understanding without so many assumptions.

This is how you figure stuff out.

That's the goal, merely saying there is another way than my so called way(which I there are many ways that I do and have done things including this one... ahem) is not going to solve or help better understand things.

Methods need to be looked at critically, not just bashing the critics or another method, that behavior is politics, not science.

A cat can only be skinned a few different basic ways, but there is more than one

Tom Barr

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Old 08-12-2004, 09:36 PM   #9 (permalink)
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I hope that I did not come off in any way as bashing your's
or any one else's method. The amount of knowledge you have
contributed to the aquatic gardening "hobby" is incredible and
immensely useful. I read all of your posts with great interest.

The way I am thinking is phosphate and nitrate cannot just
be limited, they have to be zero or as close as possible. I know
zero is physically not realizable just because of feeding, plant
leaves decaying, etc.

I think it was in your post that I read a while ago about algae not
being limited until phosphate was in the PPB range. I think this
is true. Foliar uptake should be able to easily handle this level
between water changes.

Same goes with nitrate, IMO.

I'm an engineer and hella anal-ytical . It doesn't make sense
to me how you can add PO4, NO3, K+, etc. into the water and not
expect to see algae. I have seen TV shows (I know don't trust TV)
on PBS that maintain PO4 and NO3 are metrics for pollution/algae
growth. What about the more mature reef sector that will do
anything to avoid PO4? Reefers strive for 0ppm PO4.

If you look at my moss, you can see that it is struggling. This is
a weakness of having a lean water column plus being under bright
lights. However, moss doesn't need that many nutrients to grow;
it can get it from the wood, just like real moss does in nature.

Let me know what you think.
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Old 08-12-2004, 11:17 PM   #10 (permalink)
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Default Resize Pictures

Here are the resized pics. I don't why they look so dim, I have 6wpg of NO. Is it possible for the previous photo to be deleted or my double post? Thanks.

Plenum Closeup

Corner(shown previously, but resized)
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