Drop checkers and atomizers?

[Jim Miller]

I wonder if drop checkers are capable of providing accurate dissolved CO2 measurements in tanks using atomizers/diffusers as an injection method. I often see videos of CO2 fizzies streaming across the tank and presumably entering the drop checker air chamber. Wouldn't this pollute the measurement?

I ask because I see posts of people who have changed from various reactors to atomizers and claim that they see much more rapid change of their drop checkers and with fewer bubbles per second. I could write off the bubbles per second as due to the change in working pressure delivering the same number of moles of CO2 in fewer packages. But if dissolved CO2 is what is being measured the faster change observation would seem to defy the laws of physics.

Are these people being duped by the bubbles? If so are the plants duped as well?

 

[pat w]

You might be able to test the assumption with two checkers. One setup as normal as a control. The other with a piece of material from a fine (low micron) media bag secured at the opening to prevent the co2 from passing through as easily (you might be able to slow it down but you wouldn't be able to stop it) Even if it doesn't slow it down very much, it might collect like pearling on the material which would lend support for the idea.

Pat

 

[ShadowMac]

I use my drop checker when initially setting a bubble rate just to get a rough idea before fine tuning the dosage without a drop checker. When I added an inline atomizer I placed my drop checker behind the outlet figuring this was furthest from the spray and it responded quickly. I have subsequently reduced my CO2 dosage as this way of adding seemed to be much more efficient than the glass diffuser. Probably due to smaller bubbles and improved gas exchange with the water.

The surface between the water and the air in the drop checker is the same as the surface at the top of your tank, it is just a closed system. So gas exchange takes place back and forth. The more CO2 within the air in the drop checker, the more dissolves into the solution with the pH indicator, which changes the pH of that solution thus changing the color accordingly. So, no, I don't think it would "pollute" the measurement. Drop checkers are fairly unreliable anways.They are slow to respond, the CO2 dissolved in the water enters the drop checker chamber as a gas eventually, the bubbles probably make it respond faster because CO2 that enters as a mist hasn't dissolved but it is still available in your tank for plants to use. Gaseous CO2 could be more readily available to plants for metabolizing instead of dissolved CO2 making the atomizer better than a reactor that provides only dissolved CO2. I can say I have seen a difference in plant response with the atomizer vs an inline reactor or even glass diffuser and am switching over to inline atomizers on my other tanks.

Tom has said that misting is the best way to deliver CO2 to plants, small bubbles are best. His venturi reactor is designed to provide the smallest bubbles possible to the plants. Atomizers create a nice fog that fills the tank and collects on plants. Fish are more tolerant of higher doses of CO2 in this form (according to my own personal observations). If some CO2 is dissolved and some is in bubble form, you essentially have more CO2 in the aquarium. Plants won't complain about more CO2.

 

[pat w]

Thanks for the info, Shadow. I'm installing an Atomic inline from GLA when I do a replumbing project I have planned. Nice to know you're getting the positive results(esp. since I've already bought the atomizer)

Pat

 

[Jim Miller]

Let's take the limiting case: CO2 directly passed to the air chamber of the drop checker, never passing through an atomizer at all but bubbled directly there. In this case the tank water column dissolved CO2 is obviously near zero yet the drop checker will surely show a high concentration and likely quite quickly.

I wasn't arguing that the CO2 wasn't going to be used by the plants at all rather that the drop checker may no longer be accurately measuring the dissolved concentration of CO2 in the water column. Rather it may be just responding to whatever water stream containing a CO2 mist may be hitting it and that stream may well be quite localized in the mist content.

That localized mist could give the impression that the CO2 concentration in solution is higher and occurring quicker than previous methods.

Jim

 

[nipat]

If the gas exchange rate of "CO2 gas in DC back to tank water"
is slower than CO2 mist entering DC. Then the reading may be
not as accurate as non-mist method? Just wondering, having never
tried an atomizer.

 

[ShadowMac]

you're right Jim, if the bubbles are localized the the area where the drop checker is then you are definitely not getting a reliable reading. Thats why I placed my drop checker behind the outflow of the lily pipe, it is last place the current from the outflow reaches. I was assuming you had equal distribution of the mist throughout the tank. Flow is important. It would be important to choose a good location for the drop checker as well as move it around, or have more than one to find dead spots where there is little flow and/or low CO2 availability.

that being said the "fog" from the atomizers distributes very well and does not necessarily rise to the surface, given adequate flow.

 

[SuperColey1]

Nipat - This is true. The reverse will be slower.

I'm not sure why atomisers would change the DC quicker in forward motion. I would've thought due to bouyancy that the larger diffuser bubbles would change it quickest followed by the smaller mist bubbles with full dissolved being the slowest.

I can only assume that the reason is that the smaller bubbles are staying in the water much longer and that more are getting to the DC.

Maybe I am thinking of it the wrong way and buoyancy is the wrong thing to use. Meaning that the more boyant bubbles don't reach the DC as well and therefore the fully dissolved (reactor) has the quickest reaction of all with the larger bubbles of a standard diffuser coming last?

Either way I tend to do the same as ShadowMac above and watch it for a week or 2 on a new bottle and then ignore it once I know it's steady. lol

AC