Old school co2 method.

[Marc Davis]

Brilliant, I love experiments. I'm predicting that yes, it would fill with water, can't fill with air so it has to (I think). It's like the upside down dome/tank koi viewers - they use a dome on a floating raft.

I think this is correct. If it can't fill with air, it has to either fill with water....or more co2

 

[Marc Davis]

It’s not for show tank. But if you run multiple planted tanks in a fish room or own a shop, it’s the only practical solution without running the nightmare of multiple hoses, regulators and cylinders.

Reactor and diffuser may provide efficient high co2 injection, but for low co2 injection, the old fashion is just as efficient. Plant growth is enhanced greatly with slight elevation of co2, so you get more bang for the buck by injecting low rather than high co2 and from that perspective, old fashion is relatively more efficient.

I'm using in my show tank. Ok, my tank isn't up there with some of the tanks on here but I've only been fish keeping a year and the tank is only 3 weeks old.

Here it is. I've tried to hide it behind the swords on the left. Don't think it's too much of an eye sore.

 

[zozo]

Brilliant, I love experiments. I'm predicting that yes, it would fill with water, can't fill with air so it has to (I think). It's like the upside down dome/tank koi viewers - they use a dome on a floating raft.

Did it one time with a 25 litre tank standing opside down on a frame.. Fun for a day or 2 maybe 3 or 4 than water starts to degass in the tank making it a mess with brown foamy slime gas bubbles accumulating at the top. I guessed it was oxygen etc. gasses plants etc. release into the water column. Even tried a pump bellow it so it would have circulation. But it encreased that degassing process actualy. SInce it was such a mess in short time i dropped the Gold fish skybox. But it was funny to see them swinning above the actual surface..

Repalcing the vacuum with co2 i guess the same, if it desolves it must replace with water and fill up again. I can't think of a valid reason why it shouldn't, but it's a part of physics i'm not sure of these logics apply..

But we shortly will know.. Can't take long with a small amount of co2..

 

[tiger15]

Maybe a completely crazy idea.. But seeing it function submersed, the co2 chamber full with co2 slowly fills from the open bottom up with water again while the co2 slowly dissolves. Than the floater in the bottle is your visual marker.

Now just thinking of vacuum? Placing that co2 chamber only an inch bellow the water line, suck it vacuum and it fills with water. Attach the co2 bottle and fill it with co2 from the top.. So the vacuum will be replaced with co2.

Will it vacuum up again and fill with water with the co2 dissolving?

If so there is no need to submerse the complete botlle in the tank..

CO2 dissolves better under pressure than tension. I used to run siphon tubes in my old fashion filter, air pocket tends to form on the top of the siphon tubes due to tension, so I can predict that emerged bottle under vacuum will dissolve CO2 very slowly, and not completely.

The best way to secure a submerged bottle is not to use suction cups but to drill tiny holes on the tank rim and tie with a fish line. You can let it slide up and down with changing buoyancy or put a stopper to prevent movement.

 

[sparkyweasel]

If the bottle was above the water level, yes it would suck up water as the CO2 gets dissolved, but gravity pulling that water down will reduce the pressure of the CO2, and I think that will slow the rate at which it dissolves. With the bottle submerged water is pressing up against the CO2, slightly increasing the pressure. I wonder how much difference it would make? Probably not much I guess.

 

[Marc Davis]

If the bottle was above the water level, yes it would suck up water as the CO2 gets dissolved, but gravity pulling that water down will reduce the pressure of the CO2, and I think that will slow the rate at which it dissolves. With the bottle submerged water is pressing up against the CO2, slightly increasing the pressure. I wonder how much difference it would make? Probably not much I guess.

For that matter then, you could argue that the lower you have bottle in your tank, the more pressure/dissolved co2 you get??

 

[tiger15]

For that matter then, you could argue that the lower you have bottle in your tank, the more pressure/dissolved co2 you get??

You are absolutely right. Place your bottle, diffuser, reactor or whichever to inject co2 at the lowest point to effect the highest solubilty of co2. Tension, or negative pressure, has the opposite effect of pulling gases out of water.

Solubilty of co2 is sensitive to temp and pressure and you can find many charts in the web to depict the relationship.

 

[zozo]

I was thinking the same thing, that a vacuum refilled with co2 that gravity and pressure how tiny it is would have some effect.. But why not put to the test and see how far it goess..

Was vacuum and now filled with co2..

But for € 4.75 for a can with 5 gram of co2 this is not going to be my hobby. The can is more expensive than its contents..

And indeed weight it down and let gravity play probably would help the co2 dissolve beter by the pressure.

 

[ian_m]

I think the CO2 concentration may be a tad more than the quoted 0.8ppm roughly calculated above, possibly.

You can calculate how much CO2 dissolves in water at 1 atmosphere by Conc = Pressure / solubility. For CO2 solubility is 29.41 atmospheres / mole.

Thus conc = 1 atmosphere / 29.41 -> 0.034 M

Multiplying by atomic mass of 44 gives 1.5ppm.

However it will be less (0.8ppm ) as gas will be continuously lost from surface and also some CO2 will dissociate/combine in the water to carbonic acid. Someone want to help me out how to calculate the carbonic acid contribution ?

In the end is likely to be significantly less than the 30ppm we high tech tank owners inject.

 

[zozo]

0 atmosphere is 1 absolute, in both cases water and co2 are under the same atmosphere, doesn't that equal 0?

I'm realy not that of a physic and math wizard, tho these kind of calculation were part of my education it all is much to long ago. I've forgotten what i've all have forgotten, that long. Just gave it a go with what i could find on how much volume a mol is.. To show approximately it aint realy adding that much. As you say there is much more to it having influence but it wont make that of a huge difference..

Same as land above see level has less atmospheric pressure has effect on disolved oxygen in water. But for us neglectable tiny amounts at inhabitable areas on the planet it equals by few Mg almost total saturation. You must be awfully high up in the mountains for any significant difference.

 

[Zeus.]

I'm predicting that yes, it would fill with water, can't fill with air so it has to (I think)

My CO2 reactors must get 1/4 full of CO2 by end of CO2 period all gone by next day, cant see it being any different with these jars

Diffusion from high [CO2] to low [CO2] with the limiting factor being how fast it takes to diffuse into water OFC, Boyles Law in there somwhere

 

[zozo]

Well what do you say..
3.50PM

3 hours later at 7.05pm

Not that i yet see any plants grow.. but definitively something going from the bottle into the tank and visa versa.

I wonder where we are tomorow morning.. Might do a pH profile next.. The darn thing hangs next to it anyway..

 

[sparkyweasel]

Measuring the water level in the bottle gives you an easy way to calculate how much CO2 has dissolved into the water.

 

[zozo]

Got 3 low techs, averagely i measure pH 8.5 - pH 8.3 during day times in all of them.. I didn't measure the start value of this one because actualy didn't expect much. I assume it started around the pH 8.3 as showen in above pics... But now i measure pH 7.8... Half a unit in 3 hours time..

Didn't expect that at all.. It's a 25 litre tank.. Temp is 26°C in this heatwave lately..

Remarkable result, especialy with the vacuum idea.. prediction were it should work lesser.. I'll put it to the test and see..

 

[zozo]

Ph still dropping at 7.7 currently..

 

[Zeus.]

For that matter then, you could argue that the lower you have bottle in your tank, the more pressure/dissolved co2 you get??

Yep that's Bolyes law kicking in.

Zozo
Impressive pH drop wasn't expecting that much. Does the tank with the CO2 bottle in feed other tanks? Looks like it might. If it does a pH profile of that tank would be insightfull

A small concern I have is the fluctuating [CO2] of the tank dependant on the actual [CO2] getting to the plants

 

[zozo]

Zozo
Impressive pH drop wasn't expecting that much. Does the tank with the CO2 bottle in feed other tanks? Looks like it might. If it does a pH profile of that tank would be insightfull

A small concern I have is the fluctuating [CO2] of the tank dependant on the actual [CO2] getting to the plants

It's a stand alone 25 litre tank on day light next to an east fased window with a small hob. Still dropping at pH 7.5 now..

 

[zozo]

starting at 3 pm day before and this is 8 am next day

pH 7.7 and a nearly co2 empty bottle in 17 hours.

Seems a rather effective method, is it because of the vacuum? I expected it to last several days as stated in the video.Completely underestimated it..
Lets fill it up again..

 

[ian_m]

Interesting.

What colour is your drop checker ?

You could use multiple drop checkers with indicator/solution diluted 50:50 with distilled water to read colour change at 30ppm, 15ppm and 7.5ppm ?

 

[Marc Davis]

starting at 3 pm day before and this is 8 am next day

pH 7.7 and a nearly co2 empty bottle in 17 hours.
View attachment 116640

Seems a rather effective method, is it because of the vacuum? I expected it to last several days as stated in the video.Completely underestimated it..
Lets fill it up again..

Same rate of disolvation as mine. I refill my in tank bottle from the yeast/sugar mix that has been pressurising from the previous day. Quick squeeze in the morning and I'm set for the day (check valve stopping back syphon )