CO2 and its effects

[Iain Sutherland]

Hey folks, i have a question that im hoping doesnt turn out to be a stupid one....

For the last year or so i have been trying to get my head around co2 and the cause and effect it produces. While i dont pretend to fully understand whats going on, but i am getting there, there is one thing still makes my head spin a little.

If im injecting co2 by a method that delivers it via an outlet of a filter and that filter delivers a continuous flow of dissolved/'atomized' co2 to the first point of contact lets say at the front glass, why is it that the plants at that point which are getting supposed 'unlimited' amounts of co2 all day long dont absolutely thrive even if other parts of the tank with less flow/co2 suffer??

I appreciate that flow, co2, ferts and light are all intrinsically linked and our aquariums are a whole system, yet if a spot of the tank suffers from low flow/co2 it will develop algae first so surely the other side of the coin should be true also?? I have never found this to be the case....

Any explanation would certainly go a long way towards helping my understanding.

 

[sWozzAres]

perhaps the plants at the "first point of contact" don't get enough light to take full advantage of that CO2. The CO2 that wasn't used up then moves into other parts of the tank where there is more light.

 

[ceg4048]

This is not really true. Always remember that only Klingons use light as an excuse for plants not growing well. As mentioned many times CO2 is an ethereal component. Gasses do not behave perfectly according to our plans. It is always a poor assumption that any location in the tank is receiving unlimited CO2. The gas still has to travel across the external area of the plants membrane, across the biofilm, across obstacles that are impeding it's path such as dirt or algae spores make it's way into the tissues and be picked up by the CO2 collecting enzyme. Something as simple as a poor angle in relation to the flow can throw off the entry path. It's also possible to have too much velocity at the water membrane interface which reduces the uptake rate. Since we cannot control every single velocity vector at every point in the tank, we have to make do with a general overall velocity that more or less satisfies the plants requirements. It's also true that plants' ability to uptake CO2 vary widely. Plants that are typically in the fromnt of a tank, such as carpet plants are by far, the worst aqueous CO2 feeders in the world. That's just our luck mate. Plain and simple. Other plants, like the common versions of Ludwigia, which are perhaps the least interesting, are in fact the most talented CO2 feeders, but then, they run into trouble if the CO2 concentration sags because CO2 is like a narcotic. When you supply a given concentration you must keep that level. If the availability falls off, these plants indicate their unhappiness. As plants in the tank grow, their very same changes in shapes and sizes changes the way CO2 is distributed causing a local deficiency here, or maybe improving the concentration there. Every minute of every day therefore, the concentration profile across the tank changes. When you trim or rearrange, it changes. Even if you don't do anything at all, it changes. This requires that you constantly monitor and possibly make minor adjustments to the injection rate or the lighting or the distribution method until you find a combination that gives you the least amount of change as you do (or don't do) things to the tank.

Cheers,

 

[Iain Sutherland]

Thanks clive, i figured the answer would seem obvious once i was told it When i said unlimited co2 i meant it in the sense of unlimited against what is being injected, i think i have learnt from previous clive bashings not to assume anything and definitely not to assume anything is unlimited.
Assumption is the mother of all BBA.

This also expains why in my previous tank the HC struggled more after i pointed a big old powerhead right at it... everyday another piece slots into the jigsaw. How big is this jigsaw again?

 

[Ady34]

everyday another piece slots into the jigsaw. How big is this jigsaw again?

seemingly theres always one piece missing!!??

 

[Iain Sutherland]

everyday another piece slots into the jigsaw. How big is this jigsaw again?

seemingly theres always one piece missing!!??

One piece?? i reckon mine came from a charity shop and at least a dozen are missing!! That and the next piece you put in makes you realise the last one is from another set