Measuring CO2 levels

[Henry Hatch]

I've been reading some posts relative to the problems of using kh/ph tables and possible solutions - drop checker, 1ph difference etc.

I began questioning my own co2 levels and so yesterday I constructed a DIY co2 reactor. I felt the design was going to be more efficient. I used the same bubble rate and kept a close eye on the fish. A couple of rainbows started showing signs of stress so I backed off the co2 and did a ph test. I looked at a ph/kh table and it read 177 mg/l of co2. I don't think so.

Now I'm thinking that one way to get a pretty good bead on the co2 level would be to run a high bubble rate and when any of the fish show signs of stress test ph and back off the bubble rate slightly. I can then test ph periodically to see how close I am to the stress point value. The accuracy of the ph test is not really an issue. All that matters is that when this ph test is at a certain level my fish will show stress.

Now if I measure ph and it's say .4 below the stress point value, I know I can add more co2.

I'm sure this approach may have lots of flaws, but I'm new to plants -experimenting and trying to learn. I was trying to find some way to quantify an observation and use the data.

This brought up another issue related to whether to run co2 7x24 or turn it off at night.

Tom talks a lot about the importance of co2 levels particularly with respect to algae control. I'm trying to keep the levels up. However, I assume doing that puts me closer to the point where I can harm the fish.

When I put in my new reactor my ph measured 6.0 at the end of the photo period and the fish were showing signs of stress. I decided to turn off the co2 last night although I usually run it 7x24. This morning just before the lights came on the ph had risen to 6.8. The fish appear fine. In the past I had lower co2 and higher ph but the differential at night was normally no more than .3.

I'm not sure what to do. I don't want to kill the fish with excess co2. On the other hand I'm wondering how long it will take my co2 levels to recover with such a large difference in ph level.

It seems to me that I should not have such a large ph differential between night and day and maybe I should look for an outgassing problem or something else.


Henry Hatch

 

[Tom Barr]

The relative nature of the method you are doing is fine and works.

The CO2 off at night allows less fish stress due to CO2, because it only occurs when there is also high O2 from plants, plants do not produce O2 at night, they use O2.

So you have more wiggle room with the CO2 during the day and that's the only time you need it.

Regards,
Tom Barr

 

[eddtango]

Co2

Is it better for the plants and fish to put an airstone when the lights are off? Does Amano do this too?

 

[Tom Barr]

He says he does in some cases.
I think it's not a bad idea to add circulation, which adds more O2, but why not add pure O2 to the tank at night instead like the CO2?

The air stone is cheap, but it does not add nearly as much as more flow from filters/powerheads etc, and adding pure O2 would really amplify bacteria and fish health if set properly.

I use O2 on a couple of tanks as a back up for high CO2.
Works very well.

But I like parmonious systems, adding another item that's not really needed is an issue for me.

I've never found a need nor real benefit for this.
Think about it, why even bother adding aeration at night?
Why not simply raise the spray bar or filter outflow for good current?
Then add a bit more CO2 to off set the CO2 out gassing during the day?

That makes a lot more sense.

If you have a sump, feeding it into the intake is not a big issue really, say 1 bubble a second for a 125 gal tank at night etc.
That way you do not blown out any O2 from the plants and get better water clarity as well.

Regards,
Tom Barr



Regards
Tom Barr

 

[girthvader]

He says he does in some cases.
I think it's not a bad idea to add circulation, which adds more O2, but why not add pure O2 to the tank at night instead like the CO2?

The air stone is cheap, but it does not add nearly as much as more flow from filters/powerheads etc, and adding pure O2 would really amplify bacteria and fish health if set properly.

I use O2 on a couple of tanks as a back up for high CO2.
Works very well.


Do you use medical grade O2 or industrial O2? I ask because I used to work for Medigas, which is the medical line for Praxair. The concentration of o2 is the same in both grades however the industrial grade in not guarenteed to have zero oil contaminants, but it's essentially the same gas, other then the obvious price difference.

ziggy

 

[Tom Barr]

Welding gas

The other is far more $$, and a lot harder for anyone to get/refill for use.
If you raise the turbulance for the tank, then you have less nighttime issues with low O2.

You waste more CO2 during the day, but that's easy and cheap to add more of.

Then you do not need an airstone, nor O2.
But in over stocked systems, it's advisible.

Regards,
Tom Barr

 

[shane]

Would a wet/dry filter help this problem?

 

[Tom Barr]

Not really, depends on how you set it up though.
If you add O2 inside the the dry section(sealed) and CO2, that can work well as a reactor chamber.

In a plant specific wet dry, the chamber is sealed, the over flow level is 4" or less to the top of the tank's water level.

This minimizes CO2 degasing and O2 exchange and is a bit like a canister filter.

But the added surface area of the sump area increases exchange with O2 in the air from high to low(tank water). That is different than the canister filter.
It's economical for larger tanks and well suited to put other junk out of the tank and into the sump. Also maintains nice surface clarity, no evaporation lines etc.

They are also much much easier to clean.
Most use sponges and/or floss and/or media etc in their canister.
These can be stuffed into slots in a wet dry sump and added/removed with ease and not siphoning issues, bleching, clogged media, taking off the canister top, sloshign water around etc etc

Folks do not clean their cnaisters for too long is most cases.
Wet drys make changing/cleaning media a breeze.
You have a lot more volume for media as well.


Regards,
Tom Barr

 

[Professor Myers]

IMHO the PM o2 Cycle is often overlooked !

Worst case scenario livestock suffers for it, but very often the Best case scenario is that the o2 is Adequate or "Good Enough"...

This is really no different than folks presuming their Co2 levels based on lame tables or marginal test kits.

I'm not suggesting that folks obsess over either one, but I do believe that this is another perfect example or opportunity for folks to observe ( and Practice ! ) the mechanics of Photosynthesis, and a very modest investment and effort on their part would return far greater results than clearly 80% of the gadgets, and tripe we often over compensate with.

Simple attention to detail ...! Once the lights go off the plants are every bit as greedy for o2 as they were for Co2 at High Noon. The real trick is in balancing the PH to accomodate the swing, and that age old .4* PH rule does not necessarily encompass the True Mechanic of photosynthesis in a working biotope...

My greatest challenge so far has been establishing "accurate" ORP scales for FW aquaria, and integrating the REDOX W/ Co2 administration. Too many variables will drive you bats ! Prof M

 

[Tom Barr]

You should wait 15 min for a reading and use a Calomel reference for Redox measurements.

This is what we do for sediment measurements for wetland soils.
We add CO2 for plants, we can also add O2 gas for the fish to provide a better home for them.

Few have tried this in conjuction with CO2.

A fish health study comparing these and making a CO2/O2 line that signals poor respiration potential for fish/bacteria etc would be nice.


Regards,
Tom Barr

 

[Professor Myers]

Gas reaction chambers can be multipurpose.

The tower on my trickle filter has two ports 1 for Co2 1 for o2. 30 minutes before the lights go out Co2 is shut off. 5 minutes after the lights go out. an air pump comes on repressurizing the chamber with air. 35 minutes before the lights come back up the pump shuts down, and 5 minutes later Co2 is re-pressurized. Pure o2 is useful for heavily planted systems, and high altitude though. (Folks always seem to miss the part about altitude ???) The tower does function in a Hyperbaric capacity, but I have noticed some stress crazing at a few joints. There is an obvious 1 1/2" difference in water line when pressurized. Isn't Duct Tape just the greatest ? I'll be switching to tanked O2 just as soon as my wife drops her guard ! The only real problem suffered so far is that everything in the tank is breeding with the occasional aggression that goes along with that, and We remove 1/2 a 5 gal. bucket in plant trimmings each week from a wee 65 gal. tank.

The very same could be applied to Co2 reactors, and inline Co2 reactors. Whether it's gassing or degassing fluid the results are the same, just depends on the gas introduced right ?

Whether you add a port to a trickle filter, or add an inline venturi to the output line of your canister. Most of us already have an old air pump laying around and already use timers.