View Full Version : What does... mean?
mhhauser
02-06-2006, 4:23 PM
Latley I have been reading up on planting a aquarium, and I was getting kinda of curious what the term
"CEC"
if you don't know it here is it being used in context
Zeolite - any of various hydrous silicates of aluminum that are analogous in compostion to the feldspars. Contains either sodium or calcium or both of the type Na2O2.Al2O3.xSiO2.xH2O. Can act as ion-exchangers. Has high CEC
any help
mhhauser
02-06-2006, 4:25 PM
*
What the term "CEC" means
Hannys_Papa
02-06-2006, 4:48 PM
This link explains it but it goes right over my head lol:
http://www.gsaresources.com/cationexchange.htm
CEC = Cation Exchange Capacity
CEC references the ability of certain minerals to hold positively charged ions (= cations) on their surface structure. There may be some serious implications of this phenomena in substrates, or it may be trivial, or most likely it can help a bit make cations of micronutrients and macronutrients more readily available to root hairs of plants, but also most likely it is not of major importance.
In recent years this particular flag has waved a lot around the planted tank communities, but rather like the even earlier PMDD theory, it turns out to be not quite right and certainly not of major importance. Some very successful substrates have high CEC. Other equally successful substrates do not. Therefore the rational conclusion is that the CEC is not and should be a major factor in substrate selection.
In very simple terms. It is the ability of a substrate to trap, hold, absorb, adsorb nutrients which are/can be available to plant roots.
Flourite for example is a porous fracted clay that has a high CEC rating.
Polished or epoxy coated stone type substrates have a low CEC rating.
Jay
RTR is right on!
Watcher74
02-06-2006, 11:02 PM
RTR is right on!
And as usual, makes you feel like you just missed the last three lessons in a very difficult class. :D
quenton
03-07-2006, 11:14 PM
I am curious about your aside re PMDD -- I thought this was a reasonable way to dose chemicals for plants -- or is that outdated now??
Roan Art
03-07-2006, 11:27 PM
I am curious about your aside re PMDD -- I thought this was a reasonable way to dose chemicals for plants -- or is that outdated now??
Outdated. EI, or Estimated Index, is the way to go now:
http://www.barrreport.com/forums/showthread.php?t=1
Roan
PMDD was based on limiting nutrients for algae suppression, especially phosphate. That turns out not to work. Phosphate is macronutrient and absolutely required for plants. It was a nice theory and can help with low light slow growth tanks, but its theoretical basis is incorrect, and in moderate to high light light tanks with CO2 (bioavailable carbon) supplement it will promote algae more than supress it.
Tom Barr's concept of taking care of the plant's needs first and foremost works a lot better IME. In lab-speak, it is a more "elegant" concept - if you want higher plants, provide for their needs first, then control excesses by the simplest technique available.
Roan Art
03-08-2006, 12:49 PM
Nod nod.
I have a lot of phosphates in my tap water and use *some* Phos-Guard in my 65g. Just enough that there are some phosphates, between .5 and 1.0. I don't want to wipe them all out.
It's tall (24"), low light, no CO2 and mostly low light plants. A few high light ones, but they're directly under the lighting and doing pretty well.
There's hardly any algae and I'm having to support the SAEs with algae wafers to make them happy. Plants are growing good and I'm adding ferts as well.
I wouldn't dream of using phosphate remover in my other tanks.
Roan
quenton
03-08-2006, 1:01 PM
Thanks for the responses re my PMDD question. Having returned to the hobby after
about 15 years away I have been reading lots of things, but I see now that some of
the articles were dated a few years ago. I have read the EI article, but will have
to re-read a few times I think. The ideas look good and I intend to adopt them.
Thanks again.
Tom's report was VERY illuminating! Thank you so much for posting it Roan!
the daunting feeling i had about learning to dose is greatly reduced
my only worry is getting my CO2 up to the level i'll require- which shouldn't be that hard. . .
SUPER Helpful you're the best!
(RTR your info has been priceless as well!)
i can't believe i was thinking of breaking down my whole tank to put in an eco- compltete substrate i don't need. (tell me now if i've miss interpreted the article)
cheers -Kyle
The "high-end" planted tank substrates are good (Flourite, EcoComplete, ADA) but they are not required. I really like the original Flourite, but I certainly have not changed all my substrates over to that. I can do essentially the same thing with Estes smaller gravels, with a bit of laterite (or a lot of mulm) plus a dusting of peat at setup. Once a tank is long-established, I really don't think the handling is any different between DIY inexpensive gravel and the "super-substrates". My problem is that I like the "look" of Flourite far better than my hundereds of pounds of existing gravel.
In my book, gravel (like Eheim canisters) is forever. I moved to this house going on 20 years ago - with gravel and tanks and Eheims. The gravel and the Eheims are all still here, a handfull of the tanks have been replaced.
mdowdall
03-09-2006, 11:43 AM
Howdy
Can someone explain this line to me (from the bar report linked above):
I’ve done numerous test runs over a week or three week time period using very high light (450 micromoles/m^2/sec @ 8 cm from light source)
I thought micromoles were an expression of concentration found in physiology books? Is this a typo or have I missed something here?
m
Perhaps a typo? Microwatts/square meter/sec would make much more sense to me.