CO2 & Thresholds of Limitation

[DavidR]

I was going over the Barr Reports and I got to thinking Can you have too much CO2 concentration? BR #2 infers this, while BR #4 says no. Here's a real world example:

As you may or may not know, I'm fighting BBA in my 100g. Over the course of a month, I've strictly adhered to the EI dosing regimine. I've managed to slow it down substantially, but it still creeps along. I've pruned like mad, cleaned the glass, filters, etc., covered the BBA up, massive water changes every 4 days, and have even used Flourish Excel just to see what would happen. Nothing is working. I've been running CO2 at insanely high levels. I don't have a bubble count anymore...it's more like a steady stream.

My question is, could too much CO2 be causing problems with enzymatic production (this might not be the proper terminology), or resulting in a pH that is too low for proper growth? What I'm seeing is that my plants aren't growing as well as I know they can. From what I'm reading, you only need to saturate CO2 to a certain level, and the rest is a waste. I think I've certainly pumped enough CO2 in this tank.

Here's some numbers-

Light: 275 watts PC 6700K; 5x55w PC's in #5 dice config (2 left, 2 right, one in center)
CO2/pH: 6.2 down from 7.8 out of the tap
KH: 12
GH: 18
Temp: 76-78F
Nutrients end up far in excess after recommended EI dosing
3" or so of Flourite substrate, no root tab dosing

Plants-
Various swords of large size, but they really aren't that tall, maybe about 12-14" each
Lots of crypts, one lot of Lutea is about half the size of a basketball
Lots of vals for background
Some anubias
Trying to get a S. subulata carpet going

I'm just thinking that something isn't right. I think the light is in excess for the plants true needs, but I'd like to get this mess solved before I invest more money. I was hoping the vals & swords would shade the anubias & crypts, while allowing enough light penetration for the sag, but I prune so darn much I can't get any cover going! I'd love to figure this out!

 

[Tom Barr]

Re: CO2 & Thresholds of Limitation

I was going over the Barr Reports and I got to thinking Can you have too much CO2 concentration? BR #2 infers this, while BR #4 says no. Here's a real world example:

As you may or may not know, I'm fighting BBA in my 100g. Over the course of a month, I've strictly adhered to the EI dosing regimine. I've managed to slow it down substantially, but it still creeps along. I've pruned like mad, cleaned the glass, filters, etc., covered the BBA up, massive water changes every 4 days, and have even used Flourish Excel just to see what would happen. Nothing is working. I've been running CO2 at insanely high levels. I don't have a bubble count anymore...it's more like a steady stream.

Okay, case and point, Excel does not kill BBA.
If it did, you would have found that it did, so would have I.

You can have a high enough CO2 level to cause acidic issues with plants and respiration problem, but generally this is very very high levels of CO2.
Main thing is killing fish and other critters that use O2 for respiration.
That's the upper limit.

BR 2 says according to ref's that most plants max out around 30ppm at any light intensity.

My question is, could too much CO2 be causing problems with enzymatic production (this might not be the proper terminology), or resulting in a pH that is too low for proper growth? What I'm seeing is that my plants aren't growing as well as I know they can. From what I'm reading, you only need to saturate CO2 to a certain level, and the rest is a waste. I think I've certainly pumped enough CO2 in this tank.

I think perhaps not enough plant biopmass after wards, not enough time allowed for the plants to get going and growing well.

If not, there is something you are overlooking (but still believe you have done all the suggestions)

I'm just thinking that something isn't right. I think the light is in excess for the plants true needs, but I'd like to get this mess solved before I invest more money. I was hoping the vals & swords would shade the anubias & crypts, while allowing enough light penetration for the sag, but I prune so darn much I can't get any cover going! I'd love to figure this out!

You never mentioned tank size.
Reduce the light, that will tell you a few things quickly.
You can remove some of the Anubias and place them in a bag for awhile.
They last quite sometime if kept relatively cool or place in a bucket or a terrarium etc.

Add some cheapy plants, like Hornwort, Egeria najas, Cabomba etc. Pack the tank.

Add slower growers back after the tank settles down.
Should be fine in about 2-4 weeks.

10 hours of light, 2-2.5w/gal range

Regards,
Tom Barr