[JDM]

Here is a shot of my tossed together plant only tank.... really just a pitcher that I tossed some leftover sand and duckweed into. Today I dropped in a dwarf pennywort, sprig of red ludwigia and regular pennywort stem with a tiny leaf on it. This is more a little test setup, unheated and using only natural light. So far no fertilization.

I will be periodically testing the water but it starts out today at a pH of 8.4, due mainly to the lack of CO2 in the sun I expect. I'll test the hardness later. I probably could stand to remove some, or most, of the duckweed as it's pretty think in there.

Jeff.

 

[beaslbob]

As usual looks like you're off and running.

 

[JDM]

:-D

 

[JDM]

Source water:

23dGH
20dKH

plant only jug after two weeks

15dGH
9dKH
Not related but tested: ammonia and nitrites zero... No surprise there. I didn't test nitrates, didn't want to have to shake the bottle.

It would appear that my previous conclusion from my aquarium water changes were close to what actually happened. I saw a rough 25% decrease in both GH and KH with plants in the tank and minimal fish. Once I added larger quantities of fish the change in hardness was not nearly so drastic. I attributed the initial change, after some thought and an incorrect conclusion, to the plants utilizing the carbon from the calcium carbonate that makes up the alkalinity (KH). Once the fish were added in greater numbers, the plants then used the easier to obtain carbon from the increased levels of CO2 produced by the fish.

The result in my tank is a sustained harder water with a stronger pH buffer but a lower pH due perhaps to a high fish load and higher resulting sustained CO2 levels. Typically I had a pH in the high 7's and every once in a while, 8.0. Now it is nearer 7.4 to 7.6 pH. I anticipate that as the plants grow out or I add more, that the pH may rise as their carbon consumption capacity increases faster than the fish growth produces it.

So the plant only jug has an 8ppm reduction in GH and an 11ppm in KH (57%). I almost would have expected the absolute reduction to have been closer between the two. I'm not going to theorize why they are what they are relative to each other though... it's lunch time.

Jeff.

 

[JDM]

dKH is now 8.
Didn't test GH.
pH is hovering around 8.4 still.

There is some dead plant material building up as the thick cover of duckweed finally starts to thin itself out. I'm thinking that the decomposition will bump the ammonia and, while there would be a cycle occur, it will not be typical and I probably won't see any spikes as a result. Given my extremely low nitrate buildup in my aquarium (have yet to cross 5ppm) I might expect to see none here.

I dosed a bit of flourish comp today after testing the water. Curiosity more than anything.

This weekend I may remove 75% of the duckweed... maybe more as I would leave just enough to cover the surface of the water. Debating whether to do that or let the weed figure out it's own equilibrium. The dead material will just form a mulm on the bottom and add to the ammonia source which wouldn't be a bad thing.

Also debating whether to change water or just top it off. If I wanted to have plants thrive in there I would change the water but I am curious to see how soft the water gets and if the pH can maintain it's fairly high level.

I think that duckweed would make a great addition to a planted sump filtration system. I wanted to do that from the beginning but didn't know what I didn't know at the start.

Jeff.

 

[MoneyMitch]

interesting experiment you have going here, if i were you to keep in the spirit of things, i would let the duckweed figure itself out. worse thing that could happen liek u said is a moonia spike in a planted ":aquarium" not really a bad thing with no fish in there. definately going to follow this one you have grabbed my intrest

 

[Fishnerd101]

I'd just not mess with the duckweed. Like you said, it'll eventually fix itself and this just and experiment. No harm from an ammonia spike.

 

[JDM]

I added some plants today, major trimming in the main tank so I put some java moss , dwarf hygrophila stemlets and a java fern rhizome with a baby attached. I noticed that the regular hygrophila that was already in there isn't doing too bad.

KH is down to 7. Interesting how it is slowing down... of course I now see that had I been actually intending to do an experiment properly I would have tested daily from the start and maybe stuck with just the duckweed.

Anyway, the first two weeks averaged a KH reduction of 0.79dKH per day. Now it is around 0.25 to 0.3 per day. If I were measuring the plants I could track the growth against the KH drop and gain some insight into.... something.... oh, I added top off water twice now, that may affect the KH reading a little bit. With this small a container just doing the testing removes a noticeable amount of water.

I expect the reduction is the slowing down of the plant growth. I'm not sure how the decaying material will affect the growth and uptake of KH. With the pH still pegging 8.4, I doubt that there is much free CO2 in there so I might anticipate the plants to not be doing well soon. The duckweed doesn't show any signs of a major die off though, even though it is as thick as it is.

Here's a shot, lots of disorganized green. Hard to do much scaping with so much duckweed covering everything.

Jeff.

 

[MoneyMitch]

good theroy with the kh you have there, any plans with co2 issue?

 

[JDM]

good theroy with the kh you have there, any plans with co2 issue?

CO2 issue? There's no issue there. Seeing as the CO2 acts primarily as a source of carbon, the plants get this from the KH component. When the lab tested my water CaCO3 was the primary constituent and I am certain that this is an alternate source of carbon. The slowing down may also be from the other constituents of the KH not being utilized by the plants so there is likely to be some baseline that it will not go below. Seeing as I start from a 20dKH, my baseline might be higher than someone with a 10.

I saw this play out in my main tank as the KH lowered by over 25% while there were very few fish. As I increased the fish load, thereby increasing the CO2 production, the plants continued to do well, at least as well, but the KH has not continued to fall... at least not nearly so dramatically as it stabilizes at a higher value with more fish present. I don't think that the plants are doing any better with higher CO2 than with higher KH.

I'm thinking about trying some solutions of hyper hardened water to add to the jug. Either evaporating my already hard water to increase the concentration while keeping the same contents which might serve to increase the GH more than the KH over time (TDS issue arises here) or just crush up some egg shells to provide a purer source of CaCO3... either that or play with some antacid remedies, I expect they would have other crap in them though. Eggshells would be easier and quicker than a limestone method, which could be an option.

I still wonder about the reasoning behind the CO2 injection. I am trying to stay ahead of plants that are threatening to grow out of my Aquarium (not this little jug). If I upped the light, nutrients and added CO2 I would just need to garden far more often and my expenses and time expenditure would be greater. I know there are many plants that do better with higher CO2 as their carbon source, and obviously plant only tanks would be high in the list of those that could benefit from it, but if the only reason is to provide more carbon in a useable form for the plants in the water itself, wouldn't a soluble substance that can be just added to the water occasionally be easier than having to monitor bubbles and adjusting regulators?

Having said that, I don't agree with the liquid additives with their inherent preservatives.

Jeff.

 

[MoneyMitch]

if i follow and undersatnd correctly here, your saying the plants are using the kh as thier source of carbon rather then co2? never relized or thought about that. have you noticed slower growth of this method vs injection? lower maitence is always welcomed and sounds easyier then timeing bubbles and setting up a co2 system and exchangeing ur tanks gasping fish etc etc and the ph flux.

 

[fishkid]

Some plants, such as Vallisneria, are able to fixate carbon from carbonates in the water and use that as their carbon source. However, not all plants are able to do this. Nothing matches CO2 supplementation if rapid growth or growing some of the more exotic plants is what you’re after.

 

[rockhound]

You probably know this but, KH is measuring the amount of carbonate (CO3) and bicarbonate (HCO3) in solution rather than CaCO3. It is expressed as a ppm of CaCO3 or dKH because that is the amount of CO3 or HCO3 in a CaCO3 solution of that concentration. For your KH measurement, CaCO3 is the major constituent, there are other constituents. They are all equally utilized by your plants because the plants are utilizing the CO3 and HCO3 ions and not the CaCO3.

The reasoning for injection of CO2 over the addition of concentrated carbonate solutions is twofold:
1) Generally (there are probably upper limits and special cases) higher amounts of carbon yields greater growth. CO2 is the primary source of carbon for plants. Freshwater environments tend to have very low amounts of CO2. Increasing the amounts of CO2 in the water thus increases plant growth.

2) While aquatic plants utilize both CO2 and carbonates in the water for growth, the utilization of CO2 takes no energy compared to the utilization of carbonates. Because of this plants much prefer CO2 to carbonates as a carbon source. If the aim is to increase growth of plants, increasing the CO2 in the tank is much more efficient than adding concentrated carbonate solutions.

Additionally, not all plants are even equipped to utilize bicarbonate. In Diana Walstad's book The Ecology of the Planted Aquarium she discusses that only half of plants commonly used in the aquarium trade are equipped to use bicarbonate as a carbon source. I recently purchased this book and would highly recommend it.

 

[ao]

cute bowl~

for carbon....personally I use metrocide, I can only say that it works and keeps most algae at bay. as for poisoning my fish and stuff, I dunno. my shrimps havet died yet. lol.
I think it's like ammonia, nitrites, nitrates etc, they are all toxic. but if the plants or the biological filter consumes it at a good rate, the livestock is safe. same with excel or whatever. I used it only in highlight and heavily heavily planted tanks at a double dose.

 

[JDM]

Here's a shot of the Bacopa breaking the surface of the duckweed patch in the jug experiment and a shot of the original clump of these stems. I took one, cut it so that it was just tall enough to be at the surface of the jug two days ago, and it is doing well.

I wonder if I can get this to flower this way... if so I will have an excuse to keep the jug as it will look a little more aesthetically pleasing to my wife.

I added some more sand to allow better rooting of stems as they get taller.

KH is run down to between 6 and 7... say 6.5. I thought the bottom might have been 4, and it may be, but I had to add some water due to my testing.

I did a pH test a few days ago. It's been riding 8.4 so I took a glass of water out after sundown (min CO2 concentration) and let it stand for a few hours while intermittently bubbling it to see if I could inject some CO2 into a depleted water. The second test did show a slight drop in pH, not enough to say 0.2 but enough to see a definite difference in the purple colour towards 8.2. I have to assume that is from a slight increase in CO2 concentration. This using only air. How much was from me bubbling and how much was from just surface contact, I don't know. With the duckweed mat in the jug, surface transfer would be minimal anyway.

I forgot to test the pH in the morning to see where it sits after the plants do their respiration bit and to compare it to my little bubbling test.

I may buy a small air pump and stone and bubble the jug to see where the pH ends up.

Anyone have any suggestions for a really quiet really small air pump and a fine fine stone?

I know this doesn't get the KH addition test anywhere as adding CO2 into this environment using just air would only work in a severely depleted tank. But I am curious and I have some work to do before testing anything else anyway.

I could start with fresh water, bubble in the air and compare the KH reduction from the get go.... another time, but I might expect the KH to be depleted slower, not at all or have a higher "bottom end" if the air can diffuse CO2 into the tank at a similar rate as the plants will use it.

I am looking toward setting up a plant only tank with the bare minimum of external support (filters, pumps lighting) so everything that I do here is pertinent. I've got this west facing wide window ledge in my office that would be cool to have a tank in and not have to worry about fish.

Jeff.

 

[ao]

drop a few snails in the plant only tanks, they are my favorite clean up crew.
For the air stone I actually would recommend a CO2 glass diffuser if you want it to be very fine. It works very well ^_^ and ebay is your friend on this one.

Airpump... I use tetra whisper airpump. but in general when compared to my azoo HOB and internal filter, airpumps are noisy noisy things.

very cute emergent bacopa XD if it doesnt flower come the warmer weather put a red lght over it ^_^

 

[JDM]

Yah, I remember them being noisy. Diaphragm pumps are. I'd probably have to put it on a digital timer. I know that I won't want to listen to it and neither would the rest of the family. Run it during the day while at work and the work schedules are not the same every day.

I have at least one snail in there now, but it would be a great place to drop other unexpected snails from the main tank.

Jeff.

 

[JDM]

It appears that the bottom of the KH is 6.5 while the GH stops at 15.

I only ever dosed the jug once with flourish comprehensive and, considering that the environment is mostly closed and the plants seem to be doing little more than holding their own, I doubt that adding more would have been of any real benefit. I do see that there are more emmersed leaves appearing on the pennywort and dwarf pennywort (I have forgotten what that actually is). If I were trying to do real serious science, I would not let those leaves stay above the water as they are getting CO2 from the air now... but with a small open top tank that is not a problem, in fact I would like to see something like that to provide a possible flowering display... the bacopa might, the others won’t, I don’t think.

I mixed up about 250 ml of the jug water and added 5 crushed eggshells. Largest pieces are about fine sand grain sized down to dust, shook vigorously and let stand for 24 hours.

The shell solution reached 16dGH and 15dKH representing increases of 1d and about 8.5d respectively. I was surprised that the GH did not rise similarly. Interesting.

I added this to the jug and let stand overnight. The new jug parameters are 15dGH (it didn’t move, or not enough to measure with the test kit) and 8dKH. Given the jug volume those are about right.

What might be a better test would be to setup a plantless jar with the eggshells and the planted jug with the same and do some comparisons of the KH component between the two. I would be curious what level the plantless reaches and if the planted continues the same. I may start with some RO water for the plantless rather than having to deplete the jug and basically starting over with my really hard water again.

Jeff.

 

[JDM]

Updating the plant list, no new additions though. If I really wanted to put something in that would definitely affect the KH I would use some small vals.

The primary plant is the duckweed and I suspect that it is the largest factor in all of this. Java Moss , Dwarf Hygrophila stemlets and a Java Fern rhizome with a baby attached, bacopa caroliniana , brazilian pennywort , some dwarf pennywort.... all small pieces.

Everything is green but due to the abundance of duckweed and the water level being kept low (puts it at the widest part of the jug for surface area) it's really hard to see if there is any plant growth. I'm not as concerned about that as in a small tank environment I would not be wanting huge growth. Even in the larger tank I really only wanted it initially to maximize the ammonia sinking. Slow, steady growth is a better goal anyway. I'm at the point there that I will be removing some plants... already removed a good number of the dwarf hygrophila (tossed some and moved some to the office tank).

Jeff.

 

[MoneyMitch]

where you mentioned you had a cup of water where you allowed the co2 to deplete, you mentioned you had put a air stone in to see if you could get some natrual co2 dissolved into the glass? i thought co2 was lighter then o2 thus you would lose co2 at the surface rather then gaining it. you said you noticed the test a slightly diffrent color. was this due to lighting or perecption
? or did you keep the vial from before and after then compare?