# Red plants and high tech soil tanks



## Zapins (Jul 28, 2004)

I've had a high tech soil tank going for a few months now and I have noticed that when red plants grow in the tank they seem to grow out extremely red and pretty looking. I think this is probably because the water column is nutrient poor which forces the plants to get all their nutrients from their root systems, ultimately slowing down the uptake of nitrogen (since they can't absorb N through leaves and stem), causing more red to be revealed. Also, there is the possibility that the high level of micro nutrients in the soil contributes to the increased red colors. Has anyone else seen this in their high tech soil tanks or have an idea why this seems to happen?

Tank stats:
Standard 90g
4x 54w T5 HO light (3x6700k bulbs, 1x10,000k bulb)
10 hours of light per day
2 inches of Scott's top soil, capped with 1.5 inches of fluorite 'dark'
Water changes about 50g per day

Plants that go red:
Nesea crass.
Rotala Macrandra
Rotala 'goias'
Rotala rotundifolia


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## davemonkey (Mar 29, 2008)

Funny, I was just wondering if this could be from micronutrient defficiency. In my NPT, I have only organic potting mix (no mineral substrate) capped with some playground sand. So, as far as I am aware, I should be nutrient defficient all-around except what I feed via my fish and fish food.

My _L. aromatica _used to be green except the very tips and now that it's in NPT it is dark red/maroon all over. _Polygonum kawagoeanum_ is also a very much richer red/maroon color than what it was in my high-tech EI tank. Of coarse, the tiger lily has always has dark red colors regardless.

My brother has a 125 NPT with the same substrate and had _E. tennellus _'pink' showing deep coloration through-out, even when his lighting was lower (1.25 WPG) .

In my daughter's El Natural, I'm using clay soil substrate and the "red plants" are not quite as red. Maybe some other factors though.

-Dave


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## f1ea (Jul 7, 2009)

Are you injecting Co2 or are you relying on Co2 from the soil, decomposition and fish respiration??
(this has nothing to do with the red colouring, but i'm asking just out of curiosity)


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## nfrank (Jan 29, 2005)

like Zapins says, lowering the water column nitrates can make some plants redder. Unlike nitrate, phosphate can be sequested in the soil. Plants in high light, CO2 rich tanks will more quickly deplete the water column of nutrients. So, the low light "natural" tank may or may not exhibit this behavior.

I first noticed this phenomenon in the mid 90's before water column dosing became commonplace. At that time, I mostly kept small fish populations and fed very infrequently. The largest source of macros was water changes. My stems plants were blood red. 
Check out some of these pics. The substrates were soil/sand and peat/sand. 
Neil's plants in 1999


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## Zapins (Jul 28, 2004)

Hmm, interesting.

I have noticed some paleness in certain plants near the growing tip from time to time, almost like mild N deficiency symptoms. The color seems to correct itself as the plant grows, there is no stunting at all. 

I think the high lights and CO2 are doing exactly what you say nfrank, removing nitrates from the water column completely, forcing them to rely on substrate alone for nutrients. The N deficiency isn't severe, and it never seems to progress, but its definitely as if the nitrate levels the plants are getting are right on the edge. Perhaps the light and CO2 conditions are just driving the plant to grow faster then it can absorb N from the soil?

Those colors (in the link) look nearly exactly the same as what I'm getting on my plants. I also forgot to mention I keep Limno. aromatica as well and the tops and bottoms are red, not the normal green top, purple bottom.

The plants are very pretty I must say. I'm getting consistently better colors with soil (in all my soil tanks) then I ever did with water column dosing alone.


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## davemonkey (Mar 29, 2008)

f1ea said:


> Are you injecting Co2 or are you relying on Co2 from the soil, decomposition and fish respiration??
> (this has nothing to do with the red colouring, but i'm asking just out of curiosity)


No CO2 injection, just what the soil/fish produce. Also, I have moderately high light.

N defficiency sounds about right. With soil organics, decomp yeilds straight up N (gas) from nitrogen compounds that escapes form the water quickly, so plants likely do not get much if any. I believe ammonia is the N source in these soil tanks? (I wish I had kept my college books!!)


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## nfrank (Jan 29, 2005)

It is not too hard to achieve these results without soil or rich substrate. What is needed is less addition of certain macronutrients to the water column.

First, let me say that the red stem plants in my 1999 picture (I believe they were Ammania senagalensis) were not planted in substrate. Although not easy to see, the tank was filled with 5 inch round pots and those stem plants were simply wedged between them. Moving pots around was the extent of my aquascaping during the mid to late 90's  So, I believe i what I achieved was low N, low P and a lower N ratio. (I did not and still do not test the water). There was also competition from Echnidorus horemannii and other a full tank of other plants to keep the water column low. That is probably why the Ammania had very thin stems (~1/4"). Bumb up the nutrients and the stems would be 3/8 - 1/2" (0.3-0.6mm).

When we have soil-based "natural" tanks, we tend to not add macros to the water column. On the other hand, with "hi-tech" tanks, many folks use EI or other regimes that involve regular and generous additions to the water column. There is a middle ground. I have always preferred to keep my water lean and my lighting moderate. I also have relatively softwater. I now like to add macros, but do it gingerly. _*Extra is insurance, but there are consequences to the morphology and colors.*_ Recall that when folks first started to add macros, it was only KNO3 (or NaNO3). Thats how many of us in the 90's first got started with hydroponics. It was even a big scary step for some aquatic gardeners to even to that. (search the archives of the APD or simply google this subject and you will see some funny discussions among the "experts").

Later, slowly came phosphates which were assumed to cause algae. I credit Tom Barr to correcting that myth. Tom's tap water was high in phosphate and he had fantastic plants wo algae. Thru careful study and experimentation, he confirmed that inorganic phosphate did not cause algae provided that all the other "fuel" was available. Of course, lighting and temp (and to some extent Ca and Mg) determine the speed of this engine. [ Also, with Steve Dixon of SF, they also found that low N helped keep plants red.]

What I am saying is that when we add macros, we can control the proportions. When i first started to add P (just very small amounts, say 1/8t to a 75g with water change), i noticed some interesting changes to the morphology. The leaves got wider (fatter) and maybe the colors redder. I wouldnt say the plants grew better or looked nicer, just different. Algae did not magically appear!, or atleast more than before.

Then i started to add N and P together, using (a) KNO3 and (b) K2HPO4, 4:1 by volume (sometimes in combo with NaNO3, 3:1:1 to avoid potentially excess K) . I calculated those ratios to achieve added N ratio of ~10:1. BTW, this preceded the known "named" regimes which are intended to achieve wider target ranges. (Just like the use of soil-based "natural" approach, all of these recipes make it easy for relatively inexperienced people to confidently come into the hobby and to serve a wide range of water conditions.). But they primarily focus on getting plants to grow, with various degrees of effort, and primarily without the nuisance of algae.

More recently, i have changed the a-b proportions to 3:1. Thus, I am now starting to lower the ratio to slightly favor P, and may continue further in this direction. I invite other to join the "study." By adding water column nutrients in different proportions, we should see morphology changes. Same should be true for a particular soil used as the substrate. All soils are not equivalent.  Thus, it may be hard to come up with formulaes but it can be fun to observe.

I should say, all of these numbers i mention above consider what nutrients i already provide thru regular water changes (my tap water is a nice 15:1), and with some consideration of the N from feeding and fishload. The changes i describe may also be plant species and community specific.
--Neil


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## El Exorcisto (Aug 10, 2006)

Yep, I see the same phenomenon. My R. Macrandra looks bloody, my L Aromatica is a deep maroon in new growth... Then there is my Blyxa Japonica, which shouldn't be red, but it apparently doesn't know that. New growth is bloody red...


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## nfrank (Jan 29, 2005)

for improved accuracy of my earlier post, i meant to say i use "Potassium Phosphate Monobasic (KH2PO4)."


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