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Do 'Easy' plants need 30ppm?

daizeUK

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18 Jun 2013
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161
Location
Berkshire
I know that the recommended target for dissolved CO2 is 20-30ppm. That's because of livestock tolerance levels and in an unstocked tank you can turn up the CO2 even higher - right?

What if I have a tank full of 'easy' plants such as anubias, fern and moss and very little algae. Let's assume they have around 3ppm dissolved CO2 from the atmosphere and sufficient nutrients and they grow well, albeit slowly.

Now if I increase the CO2 to 15ppm in that tank and up the ferts accordingly, what could I expect to see (assuming stable CO2 levels and good flow)? The plants would grow faster but would the algae also grow faster?

If I increased the CO2 again to the recommended 30ppm, would the algae magically disappear? Why?

I'm trying to understand if low CO2 levels will cause algae in a tank with plants that are good at utilising low levels of CO2 and whether there is any benefit to trying to achieve the magic 30ppm in this sort of tank.

Cheers,
Daize
 
The amount of co2 your plants need depends on how much light you are giving them, the less light they get the less co2 they need.
Think of algae as a disease, if the plants are healthy they can fight off the disease. If they are unhealthy due to too much light/not enough co2 + ferts/flow then they will be overcome by the disease and die.
 
I'm trying to understand if low CO2 levels will cause algae in a tank with plants that are good at utilising low levels of CO2 and whether there is any benefit to trying to achieve the magic 30ppm in this sort of tank.
Its variability of CO2 levels that cause the issue. Algae being so much smaller ie single cells, responds much quicker than the plants to changes in CO2 level (and ferts) and takes hold. Poor CO2 is both variable levels as well as poor distribution around the tank.

Use this algae response to your advantage if you have a severe algae issue, blacken tank for say 3 days, it will kill algae as they don't store food unlike the plants which will be fine.

Keep at nice, reliable and repeatable 30ppm + EI dose + limit light reasonable levels, and algae won't be an issue. Obviously if you have no live stock you may have CO2 at even higher levels, no problem.

So main thing is nice, reliable and repeatable CO2 level, which is why some of the "big boys" tanks on this site use CO2 dual stage regulators that have cost them £100's to put together. Don't forget flow around the tank either, no point having serious CO2 setup and only providing it to half the tank.

I followed the CO2 (and ferts) advice on this site and despite the odd bit of BBA on fixtures and fitting, odd BBA on "old leaves" and occasional green spot on glass not suffered any serious algae issues.
 
No plant needs 30ppm. That is us pushing as much in as we can to try and get some to the substrate. It may be 35ppm in the upper regions yet 8% at the substrate.

As per post above. The CO2ppm is nothing to do with the plants needs. It is to do with the light and the speed of growth the light drives the plants at. i.e. if Bradley Wiggins is in the Tour de France he eats a diet of 8000 calories a day (plants with high light. calories = nutrients of which C is one) If he gave up tomorrow he would need to drop down to 2500-3000 calories (plants with low light.)

So think of the CO2 at 30ppm as being a buffet. It is left there all the time and the plants takes what it wants when it can as long as there is some left.
 
Thanks for the replies!

So low CO2 by itself does not cause algae, rather it is fluctuating CO2 or insufficient CO2 for the plant's needs, as determined by light levels.

In my case I'm talking about plants that are very good at utilising whatever little CO2 they can get, under low to moderate light levels. If I've understood this correctly, I could have a lower level of CO2 with - say 15ppm for example - and as long as the CO2 levels are stable and there is good distribution and sufficient ferts then this would be all the plants needed to stay healthy and beat the algae.
 
The PPS Pro method actually suggests 15ppm CO2 rather than 30ppm. However PPS Pro is a lean dosing regime. With those sort of regimes there is no room for error. If you are going to lean dose (incluing CO2 which is a nutrient) then you end having to micromanage.

The idea of something like EI or higher dosing is that you don't have to micromanage. You add adequate amounts of things (within safe limits of course) and then sit back and enjoy your tank and scape.

Rather than thinking of stability as the total of things think more of uptake. for example if 30ppm in a setup that is perfection in terms of flow, circulation etc results in 8ppm in certain areas of the tank like the substrate and the plants need to utilise 3% of the CO2 to grow at the speed the lights are driving them at then they have no problem. If you up the light and they now need 6ppm then you should still be OK. Now drop the injection to 15ppm and say there is now 4ppm at the substrate. you are now making them work very hard to compete for the level of CO2 available to them.

Plants within the tank are pretty much like wild animals. They are fighting for survival which means the more of them there are and the more they grow the fight gets harder hence why EI or higher dosing regimes are much more succesful. They let plants concentrate on growing and not be constantly competing with each other.

Also removing the CO2 competition aspect by making it freely available means that the plants can use their efforts in other areas. You can actually use lower light with good CO2 than you can in a non CO2 tank as they can spend the energy they would normally be using up fighting for CO2 and nutrient on utilising the available light better ;)
 
Thanks for explaining that so clearly!

The idea of something like EI or higher dosing is that you don't have to micromanage.

Isn't that what the Estimative part is about, though? I thought the idea of EI was to take the maximum possible and then adjust down to suit your lighting and plant mass.
 
Not really. EI is about add more and then you don't need to worry about whether there is enough or not. in reality many may get more into things and actually start to adjust things down. Most though will do EI as you read it in the guide and continue with that. They aren't interested in calculating this or that and why should they. Not everyone is interested in that side of things. Doesn't hurt their tanks though.

Some people dose double EI. Some dose less of this and more of that. Some dose on seperate days like EI. Its each to their own.

I personally do quite lean dosing but I don't test. I either use CO2 @ full 35ppm or I don't use it at all. If I am having to clean glass or rocks etc. then something's wrong and I get upset at having to do some work :)
 
No plant needs 30ppm. That is us pushing as much in as we can to try and get some to the substrate. It may be 35ppm in the upper regions yet 8% at the substrate.

As per post above. The CO2ppm is nothing to do with the plants needs. It is to do with the light and the speed of growth the light drives the plants at. i.e. if Bradley Wiggins is in the Tour de France he eats a diet of 8000 calories a day (plants with high light. calories = nutrients of which C is one) If he gave up tomorrow he would need to drop down to 2500-3000 calories (plants with low light.)

So think of the CO2 at 30ppm as being a buffet. It is left there all the time and the plants takes what it wants when it can as long as there is some left.


Would he get covered in algae?
 
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