question for tom about Diana Walstad

[nicklfire]

Hey tom,

Question for you man. I just finished skimming through most of Diana's book Ecology of the planted Aquarium. I was interested as you mentioned her book through some of your other posts so i thought i would at least give it a read. I was bored by some of the techy stuff and honestly couldnt follow alot of it but read most of the parts about the soils and fertz and co2.

She explains in there how the soil decomposes over time and releases co2 can it can substain doing this for years she says in a piece of her book. Ok.. as a experienced keeper i can kinda follow this but i'm looking for your experienced and testings to see your input on this. Do you think this is possiable, have you done tests of your own to see if what she has tested is correct at all.

Is her low tech tank (1.5-2 wpg) and soil and sunlight tanks that she says are usually succesfull really stand that great of a chance. Do the plants really get THAT much co2 from the decomposing soil.

Just curious on your look at it.

 

[VaughnH]

"Natural" aquariums work by growing at a very slow rate, which demands CO2 at a very slow rate. I think that is why those tanks can get the CO2 they need from the substrate. Too many people have used the Walstad method for it not to work, so the only question I see is why it works. Also, I think she wrote that book long before T5 bulbs and their individual reflectors were available, so the 1.5 - 2.0 watts per gallon is much too high if you are using the newer light fixtures. These are just my opinions, of course.

 

[Tom Barr]

Hey tom,

She explains in there how the soil decomposes over time and releases co2 can it can substain doing this for years she says in a piece of her book. Ok.. as a experienced keeper i can kinda follow this but i'm looking for your experienced and testings to see your input on this. Do you think this is possiable, have you done tests of your own to see if what she has tested is correct at all.

Is her low tech tank (1.5-2 wpg) and soil and sunlight tanks that she says are usually succesfull really stand that great of a chance. Do the plants really get THAT much co2 from the decomposing soil.

Just curious on your look at it.

Well, anything you add to the tank that has food, soil etc will rot.
When it rots in the aerobic conditions, it gets oxidized via O2.
You eat reduced carbon yourself, sugars etc, then you exhale the waste as CO2.

There's some CO2 given off in a tank, but not much is from the soil decomposing relative to the amounts of CO2, in very limiting systems with a few species of plants, they can get their CO2 from the sediments, but few aquatics do this, maybe 5 species out of 400.

Still, some CO2 does come from sediments high in organic matter, the problem is, most aquatic plants do better with only about 10% organic matter.
Barko et all showed this in the 1980's.

Plants simply increase their ability to use less CO2 that's available(as long as low/limiting levels are relatively stable), it's not that soil is adding that much CO2.

She's correct partially, but not that much.
But I do not think she's trying to be entirely correct about it, just trying to extend the virtues of soil, which is not bad.

Regards,
Tom Barr

 

[swylie]

Hey Tom, what's the capacity of plants to absorb organic carbon? I know you're working on a subset of this question for Seachem right now. Besides that though, has there been any research on the degree to which plants can feed themselves with simple or complex organic chemicals from the environment?

Sugars, nucleic acids, peptides... ?

Can they live in cell culture without light and subsist entirely on exogenous nutrition?