[puopg]

Is efficiency a problem with your skimmer setup? Or do you just need to increase CO2 a bit to hit your desired pH drop?

Ability to dissolve enough CO2 or efficiency of CO2 usage?

I can drop my pH seemingly adequately, for sure to the point where livestock have problems without acclimation. And yea just increasing a little by little. I havent tried pushing it further from my current setting since fish seem happy and plants seem ok. Ill see how things go as more grows in.

As for efficiency, I so far ran a 10lb tank out pretty much out in around 45 days. So can't say it's been super efficient. I think one reason could be the water flows from bottom to top, so im probably losing out on some CO2 there. By contrast, my atomizer on my much smaller 7 gallon lasts for like 8 months, but i guess the tank is 10x smaller as well.

 

[minorhero]

Ability to dissolve enough CO2 or efficiency of CO2 usage?

I can drop my pH seemingly adequately, for sure to the point where livestock have problems without acclimation. And yea just increasing a little by little. I havent tried pushing it further from my current setting since fish seem happy and plants seem ok. Ill see how things go as more grows in.

As for efficiency, I so far ran a 10lb tank out pretty much out in around 45 days. So can't say it's been super efficient. I think one reason could be the water flows from bottom to top, so im probably losing out on some CO2 there. By contrast, my atomizer on my much smaller 7 gallon lasts for like 8 months, but i guess the tank is 10x smaller as well.

45 days is crazy! I am only running 1 drop a second, but my 10lb tank lasts about 4 to 5 months on my 120p. Are you pumping that much co2? Or is the skimmer not dissolving everything? When you say skimmer, do you mean a protein skimmer? Cause that would definitely explain it.

 

[puopg]

45 days is crazy! I am only running 1 drop a second, but my 10lb tank lasts about 4 to 5 months on my 120p. Are you pumping that much co2? Or is the skimmer not dissolving everything? When you say skimmer, do you mean a protein skimmer? Cause that would definitely explain it.

Yea protein skimmer haha. Im sure not everything is being dissolved currently as co2 swirls up and out of the chamber but it also may just be how high I have it? I figured that given how fast I can drop the pH, the dissolution mechanism was good, even given some losses.

My thinking now is maybe initially its quick to dissolve, but then as the concentration increases it gets more difficult and the efficiency of the skimmer as reactor decreases?

 

[ddiomede]

Ability to dissolve enough CO2 or efficiency of CO2 usage?

I can drop my pH seemingly adequately, for sure to the point where livestock have problems without acclimation. And yea just increasing a little by little. I havent tried pushing it further from my current setting since fish seem happy and plants seem ok. Ill see how things go as more grows in.

As for efficiency, I so far ran a 10lb tank out pretty much out in around 45 days. So can't say it's been super efficient. I think one reason could be the water flows from bottom to top, so im probably losing out on some CO2 there. By contrast, my atomizer on my much smaller 7 gallon lasts for like 8 months, but i guess the tank is 10x smaller as well.

Holy cow, 45 days?

I've had my 10lbs tank running on my 120U since the week after Memorial Day and the gauge hasn't even budged yet. If it goes through the first week of December, that'll be 6 months on that tank, so far.

I think the key was adding the reactor, but also using a controller for the solenoid. I added the controller mainly because it was too difficult to adjust the needle valve to hit the PH drop I needed, but a fringe benefit was not using as much CO2.

 

[puopg]

Yea, im doing some investigation rn on it.

So i inverted a mason jar and displaced the water with the co2 bubbles with my current setting.

The test was only carried out once in a very janky way, but im looking at around 300mL CO2 gas every 240 seconds. Or 1.25mL / sec.

I looked for leaks in the regulator and connections but nothing seems to be a problem there. That makes sense since it was leak tested prior to being installed so I wouldn't imagine to see an issue like that there.

 

[puopg]

Here's a video of the test:

120p - Inverted flask CO2 jank test

www.youtube.com

 

[ddiomede]

Here's a video of the test:

120p - Inverted flask CO2 jank test

www.youtube.com

When my controller kicks CO2 on in my reactor, that looks about roughly the same rate and size bubble I'm seeing.

 

[puopg]

When my controller kicks CO2 on in my reactor, that looks about roughly the same rate and size bubble I'm seeing.

If that is indeed the case, our rates being similar, assuming i do indeed have a loss of CO2 somewhere, Im not exactly sure where it is. The rate being equal lets say, even if im not 100% efficient with co2 with my dissolution method, the rate its leaving the regulator should be the same right? 1.5 months vs 6 months is a big difference lmao. Perhaps the controller turning the solenoid on and off?

Do you have any data around how often your controller stays on during the CO2 period? Im curious what percentage of time the solenoid is closed during the injection period.

 

[ddiomede]

If that is indeed the case, our rates being similar, assuming i do indeed have a loss of CO2 somewhere, Im not exactly sure where it is. The rate being equal lets say, even if im not 100% efficient with co2 with my dissolution method, the rate its leaving the regulator should be the same right? 1.5 months vs 6 months is a big difference lmao. Perhaps the controller turning the solenoid on and off?

Do you have any data around how often your controller stays on during the CO2 period? Im curious what percentage of time the solenoid is closed during the injection period.

Unfortunately I don't, but it might come on like 4-5 times during the photoperiod.

It just came on about an hour ago and it's still running, but will kick off in about an hour (3pm). I won't see it kick back on until almost 6pm, and then again around 9 or 10pm. It usually runs for about a half hour to 45 minutes.

 

[minorhero]

Yea protein skimmer haha. Im sure not everything is being dissolved currently as co2 swirls up and out of the chamber but it also may just be how high I have it? I figured that given how fast I can drop the pH, the dissolution mechanism was good, even given some losses.

My thinking now is maybe initially its quick to dissolve, but then as the concentration increases it gets more difficult and the efficiency of the skimmer as reactor decreases?

Any bubble that reaches the surface is just lost co2 unfortunately. They make media reactors that would be better suited for use as a co2 reactor then a protein skimmer. I believe there have been a few people who have used them down the line. I'm not sure if they are the same or less efficient then a rex griggs or cerges though. Honestly, if it were me, I would be looking to replace the protein skimmer. You are probably losing 3 times as much co2 to the air compared to a normal reactor, maybe more.

 

[puopg]

Any bubble that reaches the surface is just lost co2 unfortunately. They make media reactors that would be better suited for use as a co2 reactor then a protein skimmer. I believe there have been a few people who have used them down the line. I'm not sure if they are the same or less efficient then a rex griggs or cerges though. Honestly, if it were me, I would be looking to replace the protein skimmer. You are probably losing 3 times as much co2 to the air compared to a normal reactor, maybe more.

Well so, I can actually seal the top of the skimmer and see how much CO2 is trapped at the top over the course of the day. That seems like that would operate similarly to a true reactor, as increasing the injection rate just builds up more and more gas inside of the reactor chamber since theres no place for the gas to go.

I do agree, I COULD just go a route of a cerges or rex-griggs, but I guess im stubborn and not ready to give up on this concept just yet haha.

Ideally what I wanted to do was have a conical reactor where the water and gas entered from the top and exited the bottom, similar to things they use to increase oxygen in some lakes. Basically something like this:

 

[ddiomede]

Well so, I can actually seal the top of the skimmer and see how much CO2 is trapped at the top over the course of the day. That seems like that would operate similarly to a true reactor, as increasing the injection rate just builds up more and more gas inside of the reactor chamber since theres no place for the gas to go.

I do agree, I COULD just go a route of a cerges or rex-griggs, but I guess im stubborn and not ready to give up on this concept just yet haha.

Ideally what I wanted to do was have a conical reactor where the water and gas entered from the top and exited the bottom, similar to things they use to increase oxygen in some lakes. Basically something like this:

Completely unrelated...but I was injecting ozone into one of my reef tanks through the protein skimmer and had a continual headache. I never thought to consider the addition of ozone as a potential cause, and honestly I considered everything but that, despite the continual headache beginning shortly after starting ozone.

I went to a doctor, a specialist, had imagining of the brain done lol, and couldn't even tell you how much I spent just to have a stoner friend ask me to check how much O3 I was injecting because it can give you a headache. After looking I told him and he said I was well over what I should have been injecting and to turn it down.

About 3 days later no more headaches. 🤦‍♂️

 

[minorhero]

Well so, I can actually seal the top of the skimmer and see how much CO2 is trapped at the top over the course of the day. That seems like that would operate similarly to a true reactor, as increasing the injection rate just builds up more and more gas inside of the reactor chamber since theres no place for the gas to go.

I do agree, I COULD just go a route of a cerges or rex-griggs, but I guess im stubborn and not ready to give up on this concept just yet haha.

Ideally what I wanted to do was have a conical reactor where the water and gas entered from the top and exited the bottom, similar to things they use to increase oxygen in some lakes. Basically something like this:

I've seen that video before, it's super cool and I even bought a big plastic flask to try to make one but never got started on it. Mostly because a rex griggs is so darn simple and works just as well (in that it dissolved 100% of the co2 supplied).

I've seen protein skimmers where they have a feed line from the collection cup go back down into the pinwheel pump and otherwise seal up the collection chamber. The idea is to keep the smell in I believe. That might work for you better here. Just be sure to adjust down your co2 if you do this and watch it. If it is more efficient, you could easily end up gassing your livestock.

 

[puopg]

I've seen protein skimmers where they have a feed line from the collection cup go back down into the pinwheel pump and otherwise seal up the collection chamber. The idea is to keep the smell in I believe. That might work for you better here. Just be sure to adjust down your co2 if you do this and watch it. If it is more efficient, you could easily end up gassing your livestock.

Yea, like if I could seal the top of the skimmer properly with a pvc fitting to adapt things onto or something, I figure id just run the pump and venturi into the top instead, and then that may achieve something similar to the speece cone shown above. Then I'd get what I wanted with suspended gas being constantly churned but kept within the reactor chamber, which should improve efficiency.

Ive currently used my rubber stopper to seal the top and im gonna measure how much pressure builds up from the co2 escaping from the top. As the pressure increases, the water level inside the skimmer body should go down, so im curious exactly how much im actually losing from the top.

 

[puopg]

So as expected, here's the pressure increase when sealed pushing the water level down. The empty space is likely co2 under pressure. So i have no idea how much that actually amounts to that either exited solution or escaped before being dissolved.

First photo shows the installation height.
Second photo you can see the water level is nearly at the red neck of the skimmer.

 

[minorhero]

So as expected, here's the pressure increase when sealed pushing the water level down. The empty space is likely co2 under pressure. So i have no idea how much that actually amounts to that either exited solution or escaped before being dissolved.

First photo shows the installation height.
Second photo you can see the water level is nearly at the red neck of the skimmer.

View attachment 1048954 View attachment 1048955

I am confident there is some kind of mathematical way to determine exactly how much pressure that thing is under... but.... I gotta say, it would make me very nervous the way it is. These things are not designed to be pressure vessels, so you basically have a small bomb in your sump right now. If I were you, I would either stop using it and replace it with something else, or I would drill a hole in the collection cup area and attach a tube from the hole to the infeed on the pump so you can recycle the gas without it escaping or building up pressure.

 

[puopg]

I should prolly mention, the fully sealed chamber was just a test. You're right that its kinda scary to have that chamber under so much pressure. In normal operation, I just inserted a check valve at the top, to relieve the pressure once it builds too high.

So lets backup real quick:
=====================
I should backup and realign on what it is that I'm actually here to prove / investigate.

The primary question I set to answer is: "Can a protein skimmer be utilized as a CO2 reactor?"

The mechanics seem decent at a glance:

• It uses a venturi and needle wheel impeller to chop gas into tiny bubbles, increasing surface area.
• It swirls and moves water in a tall chamber, so that increases CO2 gas hang time and total surface area the gas is in contact with the solvent (water).
• Given its placed in a sump, co2 enriched water exits the skimmer, and flows through the rest of the sump and then returned with minimal microbubbles. (So far, I don't really see any in the display)

So aside from the aesthetics, in essence it seems like it should work right?

Ok back to the main thread:
========================

That said, this test was done to identify the following:

1. Can my rubber stopper correctly seal the chamber?
2. Is gas leaving solution and is some gas not being fully utilized?
3. How much gas is in excess or not being used?

I believe the answer to #1 is YES. Otherwise, gas would be finding a way out and not build enough pressure to push the water level down in the skimmer body.

Answer to #2 is also YES. Clearly gas is building up, and given #1, the gas that is there is likely CO2. I think its probably a combination of gas exiting solution as well as some not getting dissolved and simply bubbling out at the top.

To answer #3, given that gas is compressible, volume really doesn't seem like an adequate measurement of how much gas is in that empty space. However, I can determine how much gas I need to add to achieve the same pressure buildup, and using the rate of gas injected, perhaps I can get an idea of how much im losing.

So, instead, I shoved a check valve on the top and ran the CO2 line directly into the top and measured the time it took to achieve a similar pressure level.

Results
======

It took about 2 minutes to build up enough pressure to cause a similar water level drop. Nothing changed about my injection rate. I also then performed a more thoughtful inverted flask test to get a better reading of my volume/time injection rate.

Video shows:

- CO2 on for ~3 minutes before flask is filled with 200mL of gas at atmospheric pressure.

Which gives us:

Estimated Injection Rate: 1.11mL / sec // (Similar to what I saw in my jank test)

Neglecting that as pressure in the skimmer body that builds up may reduce the gas flowing out of the regulator, my estimate of how much gas im losing each day is about 133mL of CO2 gas at atmospheric pressure. Some online research gives me:

"Carbon dioxide weighs 0.001836 gram per cubic centimeter at 25C, standard atmospheric pressure"

So volume of gas to mass of gas gives us:

0.001836 g / mL * 133mL = 0.24g CO2

0.24g is equivalent to 0.000529 lbs, so armed with that, lets say per day I lose 0.24g of CO2, it would take me 2000 days to lose 1 lb of CO2 from this inefficiency.

Perhaps theres some stuff in my calculations im not accounting for, or simply that my calculations are just not correct at all, but I dunno, overall on paper I feel like the amount of CO2 lost is pretty small?

Conclusion:
=========

Scoping the data to the skimmer and its ability to dissolve CO2 gas, I feel like it's performing that task. I definitely am using a high injection rate, which perhaps in conjunction with other factors such as the overflow, surface agitation, etc could be a reason why? But efficiency wise, the above tests lead me to believe the skimmer turned reactor isn't that crazy of an idea. I feel like this goes inline with my daily pH graphs as well, being that my pH drops pretty quickly, though I have very little data around what other people typically see.

I feel like if the skimmer was unable to dissolve co2 efficiently, wouldn't I expect to see more gas buildup? Perhaps my math and tests aren't valid? Or perhaps I'm missing another piece of the puzzle?

Either way, this much i do know. The skimmer CAN work. Whether or not its efficient in its usage of CO2 gas is still to be determined. However, a little digging into the past, there are some threads on barrreport where Tom Barr also uses this inverted flask technique and he has very similar injection rates. (A different method to measure CO2 at VERY high bubble rates). In fact, his injection rates are even higher than mine (At nearly 2.0 mL/second).

Videos of my tests:
===============

CO2 pressure buildup in skimmer recreation test
-

CO2 inverted flask test
-

 

[puopg]

Little update without pics:

A few things I have seen in the tank.

• Theres some patches of cladophora algae I have seen. Gonna see what happens, but so far I've just manually removed it, but next water change im planning to hit it with some H2O2.
• Saw a hydra on a rock.
• Nerite snails are laying eggs, so I think im going to remove the females from the tank if I can find em. Now I understand why I kept seeing snails on top of one another.

 

[Savannaqua]

I thought Nerites needed brackish water to breed. Maybe the eggs won't survive? Anyone know? (I'd sure like to know as I am considering them and am not a fan of snail outbreaks). Even overloads of some species of snail eggs can look lousy, whether they hatch or not.
Looking forward to the tank pics when they come.

 

[minorhero]

I thought Nerites needed brackish water to breed. Maybe the eggs won't survive? Anyone know? (I'd sure like to know as I am considering them and am not a fan of snail outbreaks). Even overloads of some species of snail eggs can look lousy, whether they hatch or not.
Looking forward to the tank pics when they come.

They don't breed successfully in freshwater but the white eggs they leave behind are noxious and stay around for a very long time in my experience.