# DIY CO2 for 75 gallon (and others) Build Thread / Performance Reports



## burr740 (Feb 19, 2014)

Decided to hook up a bit of CO2 for my 75. :bounce:

Not sure if I actually want CO2 on this tank or not, but I have been thinking about it. So before investing in a pressurized system, I decided to hook up a bit of DIY to see if I can get a feel for how things react.

Im aware of the challenges when it comes to DIY on larger tanks. Im just hoping to get a consistent 15 or so ppm - using minimal bottles. I believe that is possible with a leak free system and good diffusion.

Ive been experimenting for a few months on a 20 gallon using a single 2L bottle. I found that the following recipe will run 16-17 days, before starting to slowly taper off. After 3 weeks, it's still generating a lot, just not as much as originally, like 2 bubbles every 3 seconds instead of 1 per second.

So considering a duration period of ~2 1/2 weeks, before a slow decline, I decided to start out with three 2L bottles. The plan is to change out 1 bottle every week. Im willing to go to four and change two/week, perhaps using a bit more yeast, but Im hoping that wont be necessary.


*The Simple Recipe:*
2 cups sugar
1/2 Tsp regular baking yeast
1 Tsp baking soda

I activate the yeast first in a small bowl of luke warm water. Sprinkle in a tad of sugar and stir it gently with a fork. Then let it sit for about 15 minutes, stirring it again every 5 minutes or so. In the meantime I mix up the sugar/soda/water in the 2L bottle. I fill it about halfway with room temp water and shake it up well. Very well. Then fill it the rest of the way up (to just above the top of the label) and shake it again until everything is dissolved good. Then I pour the yeast mixture in. I dont shake it up any further.


*Now on to the build pics...* 

Here is the finished gas separator/bubble counter, a 1.89L Juicy Juice bottle with a big wide cap. That was important because I wanted the lines going in separately, to be able to tell exactly what each bottle is doing.











To create the seals, I used a combination of check valves, and air tubing connectors, the kind that come with those cheap discard-a-stone diffusers, like you see in the picture ^. Having a check valve on each reactor bottle allows you to disconnect one without de-pressurizing the entire system. 

It is based on the following method (Thanks to DarkCobra, who I believe originally came up with it some time ago)












15/64" hole
Push tubing through
Insert the connector, which expands the tubing in a tapered manner
Push it back into the cap, HARD

100% mechanical. No mess. No leaks.


*Finished separater top:*











*Finished reactor bottle cap:*











*All hooked up:*


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## burr740 (Feb 19, 2014)

Diffusion is kind of a two stage event. First there's a piece of regular cotton ball packed tightly into the CO2 line, which then runs into the intake of a small, upside down power head.




































Hard to tell in the pic because my light is aimed mostly toward the back, but the power head is mounted at the very front of the tank. The bulk of the mist stream hits the ground about where the center Crypt is, and then sorta just disperses all over. I think it is pretty efficient. You can barely see any bubbles unless you get right up close. Then it looks like a Sprite can exploded in there.

It's been running now for two days. Already seeing a bit of pearling, mostly from the Ludwigia and Bacopa. I only have med light (2 T5HO) so Im not really expecting to see much. Everything seems to have really perked up though, that much is obvious. Tops of the Mermaid Weed turned a different color virtually over night.











I havent done a full degas test with the same water yet, but PH seems to be down about .7 from what it normally is (taken in the middle of photo period) Correct me if Im wrong, but that's like low 20's ppm? If so that is fantastic. I'll know more in 24 hours.

Also ordered a glass ADA drop checker from Amazon, apparently gonna be 2-3 weeks before it arrives though :/


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## tricken (Jun 27, 2013)

it will help but with a tank that size you will want a bottle soon i did diy for a good 90 days it was fun but then mixing every week sucked.


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## mistergreen (Dec 9, 2006)

The little bottle isn't going to add much CO2 in a 75G. The 3 bottles is best for a 30G. Maintaining them will be a pain.

Your plants look great with what you have now so the bottle might give them a little extra CO2.


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## FishieNewbie (Jun 4, 2014)

awesome!!! how did you maintain such healthy plants without CO2? I am a newbie and from what I am finding so far, lighting and CO2 are what we need to get a beautiful tank like yours.


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## burr740 (Feb 19, 2014)

FishieNewbie said:


> awesome!!! how did you maintain such healthy plants without CO2? I am a newbie and from what I am finding so far, lighting and CO2 are what we need to get a beautiful tank like yours.


Thanks. The main thing I did was spend a lot of time reading this forum! :red_mouth

Lighting is obviously important, but most important is to have the right amount, as in, enough but not too much. Tons of plants out there that will thrive under low to medium lighting (what I have) and no CO2. 

Check out this thread there are hundreds of examples- Low -Tech Show and tell


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## Hoppy (Dec 24, 2005)

A 0.7 drop in pH due to CO2 means the ppm of CO2 in the water went up by a factor of 10 to the .7 power, or about a factor of 5. Assuming the water had 3 ppm before the CO2 was added, you would have about 15 ppm of CO2 now. For low medium light that may be all the plants can use. But, I don't recall anyone reporting on test results to see what ppm of CO2 is optimum vs light intensity. It would be an interesting test to try, but difficult to do well.


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## burr740 (Feb 19, 2014)

Thanks for the info, Hoppy. I arrived at the low 20s going by this bottom right chart, which seems to use a slightly different multiple somewhere.


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## Bandit1200 (Dec 11, 2010)

Before I went fully pressurized this is almost exactly what I had set up for my 29G. At that rate you will have a pretty steady flow of CO2. It did not strike me as being particularly difficult to keep up with changing out one bottle every weekend while I was doing other tank maintenance. By doing it this way you always have at least 2 bottles pushing a good amount of CO2 and by using the check valves for each bottle, you don't lose any time regaining pressure from a swap.


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## Hoppy (Dec 24, 2005)

burr740 said:


> Thanks for the info, Hoppy. Around 15 ppm is the target range Im shooting for, consistently of course. I arrived at the low 20s going by this bottom right chart, which seems to use a slightly different multiple somewhere.


That bottom right chart is incorrect. It assumes that the ppm of CO2 is directly proportional to the pH drop, and it is actually proportional to 10 to the pH drop power. A .5 drop in pH actually means about 9.5 ppm of CO2.


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## burr740 (Feb 19, 2014)

Thought I'd post an update, since it's been about a month. Still running 3 bottles, changing 1 per week. Plants have really exploded. Im having to prune the ludwigia and bacopa every week because it hits the surface. Drop checker stays a relatively darkish green, slightly brighter when the lights first come on. 

Between that, degas test, ph/kh chart, Im fairly confident in a ppm of at least 15, maybe a tad higher. Regardless, it's made a huge, HUGE difference in the growth rates and color of things.

Here's a couple pics. Ive re-arranged the tank some since the last ones.










Drop checker at the end of photo period. Picture-wise it's a fairly accurate color representation, maybe a shade lighter in person.


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## burr740 (Feb 19, 2014)

Here's a little growth update, 9 days since the last pics.










Gonna have to bush hog the back right corner pretty soon. I cut the Bacopa back a few days ago. It had hit the surface to the point it was shading the L Glandulosa.


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## korbinavery (Dec 11, 2012)

*So?*

First off, gorgeous tank! I've came back to this thread multiple times. I also have a planted 75 and have duplicated your method as it is simple and straight forward, how has it worked out for you so far?


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## Maryland Guppy (Dec 6, 2014)

Thinking of a DIY CO2 option also.


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## burr740 (Feb 19, 2014)

korbinavery said:


> First off, gorgeous tank! I've came back to this thread multiple times. I also have a planted 75 and have duplicated your method as it is simple and straight forward, how has it worked out for you so far?


Im glad this thread has been of some help to you 

It has really worked great. Ive been very pleased with the results, esp for a tank this size. Never had any algae issues, or any other nightmare usually associated with DIY CO2.

About a month after the last post itt, I increased it to four 3 liter bottles, changing out 2 per week. Also switched to using a reactor instead of a power head for diffusion (no more sprite water!)

Here's a few pics. These are probably the last ones of this tank using DIY, I have all the parts for a pressurized system, just havent hooked it up yet.




















Needs a trim:










Post trim:





























Maryland Guppy said:


> Thinking of a DIY CO2 option also.


It can definitely be done. The main things are a leak free system, good diffusion, and multiple bottles with staggered start/change times to maintain a consistent bubble rate. I was averaging in the range of 26-30 bubbles per 10 seconds with the three 2 liter bottles. Using the four 3 liters, Im averaging 39-44 bubbles per 10 seconds, or right around 4 bubbles per second. That is as consistent as Ive been able to get it, not bad for DIY iyam. Thanks for having a look


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## Dan110024 (Jul 14, 2014)

If this setup doesn't convince someone that DIY CO2 doesn't have to be messy or difficult, I don't know what will. How have you found making up a mix every week? I hear some people complain, saying it's too much work, but I have always loved tinkering and looking for something to do with the tank.

This thread has topped it off for me. Time to get a second tank setup!


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## burr740 (Feb 19, 2014)

Dan110024 said:


> If this setup doesn't convince someone that DIY CO2 doesn't have to be messy or difficult, I don't know what will. How have you found making up a mix every week? I hear some people complain, saying it's too much work, but I have always loved tinkering and looking for something to do with the tank.
> 
> This thread has topped it off for me. Time to get a second tank setup!


Thanks, mate. Im glad to hear that.

As for the task of changing bottles once a week, it only takes about 10 minutes, and most of that is just waiting on the yeast to proof (Im still just using regular bakers yeast) I also like tinkering with tank related things, so I dont mind the bit of extra work.

Having a check valve on every bottle is a big help, because you can disconnect them at any time without depressurizing the whole system. I usually do the changing out at the end of a photo period. That way by the time lights go on the next day it's kicking full strength again.

The main draw back is cost in the long run. With the 3 liter bottles Im using 2.5 cups sugar, and a heaping 1/2 tsb of yeast. So that's 5 cups of sugar and probably 1.5 tsp of yeast per week. Fast forward 10-12 months and you could buy an entry level pressurized system for the money spent. Extremely low start up cost though.


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## Wasserpest (Jun 12, 2003)

Nice postings. Uncomplicated and really inspirational. CO2, whether it comes from fermentation or a pressurized bottle, makes a huge difference for plants, at any aquarium size.

There was a guy from India who had something like a 350 gal tank with DIY CO2. :hihi: He shut it off during the night, and collected the CO2 that was produced during the night in collapsible containers, which were weighted down with bricks, so over the course of the day they would deflate.

I used to do DIY CO2 on my 100gal tank. After a year or so, I just invested in a cheap 10lb bottle, regulator, and solenoid. It wasn't as much the cost of sugar and yeast, as the weekly bottle washing and changing that got me in the end. :tongue:


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## burr740 (Feb 19, 2014)

Thank you for the kind words Wasserpest. And holy crap at DIY on a 350 gal tank, I bet that was site to behold...

-------------

Ive now gone pressurized on the 75 gallon. Still doing it on my 20H grow out tank though, the one I experimented with initially before setting it up on the 75. Just now I dug out some pics for another thread, so I figured might as well post some shots in here as well.

In particular I wanted to point out a little known fact, that Aquaclear HOB filters make an excellent CO2 diffuser. Specifically due to the way water passes through the media, from bottom to top. Other HOBs, any cartridge types, they dont work because the co2 can off-gas in the rear water chamber.

AQs on the other hand, can offer 100% dissolution, esp when pre-diffused with something like a cotton ball or chopstick in the end of the co2 tubing. This is an AQ20 @ 2 bubbles per second. Any bubbles you see are from plants pearling, zero coming out the filter. Im sure larger models could handle more.

Here's a few pics. Ive since switched to using a 3/4" piece of chopstick in the co2 line, these were taken using a cotton ball.


First planting











3 weeks











To clean up the look of things, drilled a hole and ran the co2 line up higher in the intake











Lights are two 18 watt 5000K spiral CFLs in aluminum dome reflectors. I used 23 watts for a while but they were a little too much. This tank is mainly used to propagate cuttings and experiment with different things, so the contents vary.











Not counting plants, I put this tank together for roughly $100. Petco $1 per gal sale, Aquaclear20, Black Diamond blasting sand, Clamp-on reflectors/cfl bulbs from Lowes, misc DIY co2 components...


Currently runing two 1.89 liter Juicy Juice bottles, same recipe as in OP, changing out one bottle per week.


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## benealing (Jan 9, 2015)

What size hole did you drill, and how did you attach the air line tubing? Also, what are you referring to when you are talking about prediffusing with a chopstick or cotton ball? Where do you put it etc?

Looks great! 

Ben


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## burr740 (Feb 19, 2014)

benealing said:


> What size hole did you drill, and how did you attach the air line tubing?


I _think_ I used a 1/4" bit, maybe 15/64." Basically whatever size will give you a snug fit around your airline tubing, but not so snug that it becomes a pain to get in and out. It wont matter if you go a tad over, a little water getting pulled in right there doesnt hurt a thing.

It's not attached, per say. It's just sticking through the hole in the intake tube, about halfway in. You can see it in the picture above with the red arrow.



benealing said:


> Also, what are you referring to when you are talking about prediffusing with a chopstick or cotton ball? Where do you put it etc?


There is a piece of regular cotton ball stuffed tightly into the end of the co2 line, like you see here. I do the same thing with the Aquaclear, except now Im using a 1/2 piece of chopstick. (a bamboo chopstick, just like you'll find in most any Asian restaurant or the grocery store)











This accomplishes two things: Better diffusion and no noise. 

Diffusion wise, it allows the propeller to work against a bunch of small bubbles instead of one big one. (hence the term pre-diffuse) It was getting near 100% diffusion with just an open line, but there were still a few small bubbles coming from the filter outflow. Also with an open line, there was a distinct "chirp" sound every time a bubble hit the prop.

Once I started using the cotton/chopstick, no more chirp sound. There is only a slight fizz-type noise that you have to get up right up close to hear. Also diffusion became 100%, with zero bubbles coming from the filter's outflow.


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## benealing (Jan 9, 2015)

Wonderful. Thank you for your quick reply. I will let you know how it goes. I love the AQ filter. I replaced a Whisper. I also have a 20H that I is just getting started.

Ben


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## burr740 (Feb 19, 2014)

Yes keep us posted. Another user just started doing this with some pretty fantastic initial results.

Here is the thread if you want to check it out. Aquaclear talk is sorta scattered throughout - http://www.plantedtank.net/forums/showthread.php?t=810874


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## quiquik (Dec 13, 2013)

Forgive me if I'm off subject, I would like to know what kind of plant is on the far right of your tank towards the front. The picture with the co2 line drawn in red. Thanks


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## burr740 (Feb 19, 2014)

quiquik said:


> Forgive me if I'm off subject, I would like to know what kind of plant is on the far right of your tank towards the front. The picture with the co2 line drawn in red. Thanks


It's regular baby tears, Micranthenum unmbrosum


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## benealing (Jan 9, 2015)

So I did use a 1/4 inch bit and it works fine. I also used a chopstick and really like that. 

I am noticing a few things. First off, in the AQ intake, at the elbow that turns down toward the propeller, I get a fairly large CO2 pooling bubble. I am not sure what, if any, impact it is having. Any idea on if it is a bad thing? I can make it go away if I turn the flow all the way up. I am using an AQ 70 on my 20H and the full flow seems like it may be a bit much for my tank.

The second thing is, I have two sponges as the filter. I feel like I am getting a lot of CO2 bubbles entering the water. I am not worried about the CO2 level, but I wonder what is different between our set ups. You don't seem to get much sprite water from CO2. Any ideas? Maybe my BPS is too high? Maybe I need a different sponge media?

I will try to get a picture up when I get home from work.

Thanks for any feedback. I love the design!

Ben


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## burr740 (Feb 19, 2014)

Mine will also pool in that first elbow if I cut the flow down. Ive never ran it that way for very long so not sure what the overall impact would be. I would think, as long as it doesnt get to the point of overload, where the bubble continues to grow and large portions are getting sucked into the filter...a small build up right there wouldnt affect much. It's still going to be dissolving.

As for the micro bubbles. The media in mine goes from bottom to top; sponge, purigen, ceramic bio rings (ones that came with the AQ). I have also used activated carbon in the middle section. Same difference. 

If you only have two sponges in there, maybe a good idea to put something in the top section too. The media plays a big part in keeping the micro bubbles trapped long enough for them to dissolve. The easiest and cheapest thing you might try is some filter floss. Polyester pillow stuffing works great. Just put a big wad of that in the middle section and move one of the sponges on top to hold it in place. But any kind of additional media would probably help.

I really appreciate the feedback. Very interested in other peoples experiences..


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## RedIrocZ-28 (Oct 24, 2006)

I have a question for you, or anyone here really I guess.

Why are you using baking soda in your sugar water mix? Are you using it to keep the krausen down so you don't have a blowout in one of your fermenters?

As a side note... I'm considering something that only someone who has too many hobbies that strangely have overlapping needs could do. I'm thinking that I can use fermenting wort or cider as my source of CO2 for a DIY setup. Imagine that setup, I brew beer, and get a free DIY CO2 injection source.


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## burr740 (Feb 19, 2014)

Baking soda is to stabilize the mixture by controlling acidity, which can kill off yeast. With hard water it may not make much difference. My tap is fairly hard, around 10dkH, and it does seem to extend the life by a few days. Im sure someone else can explain the exact science better than me.


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## RedIrocZ-28 (Oct 24, 2006)

burr740 said:


> Baking soda is to stabilize the mixture by controlling acidity, which can kill off yeast. With hard water it may not make much difference. My tap is fairly hard, around 10dkH, and it does seem to extend the life by a few days. Im sure someone else can explain the exact science better than me.


I've never heard of such a thing before. In my experience with yeast, the pH of the wort (sugar water) is never even a factor that is considered. 

I just did a little research on google to confirm my thoughts. I'm questioning adding baking soda because salt is what kills yeast, ever heard of Vegemite? Vegemite is live yeast that has had salt added to pop the cell walls, killing it. Baking Soda is NaHCO3, which is a salt. I'd wager that your reactors lasted a few extra days because the yeast was being slowly killed off, making the reaction less vigorous.


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## BruceF (Aug 5, 2011)

The baking soda is simply to slow down the rise in ph. 

Salt has a retarding effect on the activity of the yeast. The cell wall of yeast is semi-permeable, and by osmosis it absorbs oxygen and nutrients, as it gives off enzymes and other substances to the dough environment. Water is essential for these yeast activities. Salt by its nature is hygroscopic, that is, it attracts moisture. In the presence of salt, the yeast releases some of its water to the salt by osmosis, and this in turn slows the yeast’s fermentation or reproductive activities. If there is an excess of salt in bread dough, the yeast is retarded to the point that there is a marked reduction in volume. If there is no salt, the yeast will ferment too quickly. In this sense, the salt aids the baker in controlling the pace of fermentation. Nevertheless, we should note that a careful usage of yeast, control of dough temperature, and the type, maturity, and amount of preferment used are better tools for fermentation control. Salt quantity, as we have noted, should stay within the 1.8–2% range.
http://www.kingarthurflour.com/professional/salt.html

Yeasts are active in a very broad temperature range - from 0 to 50° C, with an optimum temperature range of 20° to 30° C.

The optimum pH for most micro-organisms is near the neutral point (pH 7.0). Moulds and yeasts are usually acid tolerant and are therefore associated with the spoilage of acidic foods. Yeasts can grow in a pH range of 4 to 4.5 and moulds can grow from pH 2 to 8.5, but favour an acid pH (Mountney and Gould, 1988).

In terms of water requirements, yeasts are intermediate between bacteria and moulds. Bacteria have the highest demands for water, while moulds have the least need. Normal yeasts require a minimum water activity of 0.85 or a relative humidity of 88%.

Yeasts are fairly tolerant of high concentrations of sugar and grow well in solutions containing 40% sugar. At concentrations higher than this, only a certain group of yeasts – the osmophilic type – can survive. There are only a few yeasts that can tolerate sugar concentrations of 65-70% and these grow very slowly in these conditions (Board, 1983). Some yeasts – for example the Debaromyces - can tolerate high salt concentrations. Another group which can tolerate high salt concentrations and low water activity is Zygosaccharomyces rouxii, which is associated with fermentations in which salting is an integral part of the process.
http://www.fao.org/docrep/x0560e/x0560e08.htm
or something like that.


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## burr740 (Feb 19, 2014)

Thanks guys, that's very interesting. ^^

------------------

A few of us were brainstorming in another thread different ways to use AQ filters. Turns out, the air hole inside the chamber works just as well as going into the intake pipe. 

This is a much cleaner application.












Just going to quote a couple posts...



burr740 said:


> So I upgraded to the AQ30 and trying out a different way to do it. Instead of using the intake, using the aeration hole in the removable plate that sits just above the impeller. It's a perfect fit.
> 
> 
> 
> ...





burr740 said:


> That's good to hear, benealing. I didnt even think about using the flow control hole in the lid.
> 
> PH tests:
> 
> ...


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## burr740 (Feb 19, 2014)

So I set up another little temporary tank using AQ filters and ran the CO2 line a bit differently. The tank is in an enclosed space and getting into the back of the filters is a pain. Also didnt want to drill the intake tubes.

Here's some pics. It's a 20L with dual AQ 20s, each working as a diffuser. Using two 2 liter bottles, changing out one per week.













Chopstick











I just split one bar in half and pushed it apart. It can be pushed back in place almost like nothing ever happened if need be.





























The purpose/point of this tank can be seen itt - Heavy Root Feeders - Fact or Fiction?


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## keymastr (May 25, 2015)

Well, you have inspired me to give DIY another shot in my 20H. I have everything in the closet for the build so I should be able to put it together tomorrow. The last piece of the puzzle for that tank is co2 so I might as well do it at least until I finish gathering the parts for a pressurized system.

I was running it on that tank a couple years ago but had a blowout and my living room smelled like a brewery for a few days. After that my wife was not too excited about starting it again, ha ha.


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## keymastr (May 25, 2015)

So far so good. I started it a little over 24 hours ago and I am getting a steady 1 bubble per second, which is not all that much but it is making the aqua-clear hiss steadily. No bubbles can be seen in the outflow so I assume it is being completely dissolved like you had experienced. I also think I need to get some better check valves. These ones are the cheap plastic ones they sell at Petsmart and they seem pretty restrictive.

How many bubbles per second would you expect to get from 2 2 liter bottles?


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## burr740 (Feb 19, 2014)

Hey keymastr. Glad this thread inspired you to give it another go. 

For me, a 2 liter bottle usually produces slightly over 1 bps, for a couple weeks before starting to slow down. Currently have two 2 liter set-ups going, and they both run about 2 - 2.2 bps.

That's using 2 cups sugar, 1/2 tsp regular bakers yeast, and 1 tsp baking soda.

Ive never used anything but the cheap plastic check valves for DIY, but I have found that different kinds will affect the bubble rates. The clear plastic, spring operated ones seem to have the least resistance. They let it run at a faster rate than the flapper type. 

But also the bubbles, in theory, should be smaller, because it's taking less pressure to crack. So different check valves can change what you're seeing, but they shouldn't have any effect on what the system itself is producing. In other words 1 bps for you may not be the same as 1 bps for me.

All you really need a bubble rate for is a reference point to keep an eye on consistency. Measuring the PH drop between degassed tank water and actual tank water is the best way to get a general idea of the actual CO2 levels. Shoot for a 1.0 drop.

Or you can just watch the plants for good growth, pearling, etc.


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## keymastr (May 25, 2015)

Well my Apon is pearling nicely and it looks like I have about a .5 to .7 drop in ph. Just using a test kit until my new digital meters show up but it looks like it went from 7.4 to 6.8 or so. I think it has loosened up the flappers of the check valves a bit also since it seems like the bubbles are a little smaller and the AC is making more of a hiss than chopping serious bubbles. 

I think I am only getting one BPS because I may have a leaking bottle. I plan on re-doing each one as they need changed and that should eliminate any issues. I also plan on running each line to the bubble counter to be able to monitor each bottle as you have done but also it will eliminate an airline tee which should be less restrictive.

Thanks again for the tips and inspiration.


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## Rinfish (Aug 16, 2015)

Thank you for posting this!!


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## Nick00Merlin (Sep 29, 2015)

I was wondering if Brewers yeast would work? Has anyone tried it?


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## AbbeysDad (Apr 13, 2016)

Nick00Merlin said:


> I was wondering if Brewers yeast would work? Has anyone tried it?


It's said that brewers yeast is better than bakers yeast since it holds up to alcohol better so the mix will last longer. However, I don't know how much longer. Active brewers yeast is harder to find and more expensive. I found some on Amazon but it was $7 for 6 grams (1 tsp = 3.15g). Perhaps there are better deals?....but it would be nice to know how much longer it really lasts.


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## cryminy (7 mo ago)

burr740 said:


> Decided to hook up a bit of CO2 for my 75. :bounce:
> 
> Not sure if I actually want CO2 on this tank or not, but I have been thinking about it. So before investing in a pressurized system, I decided to hook up a bit of DIY to see if I can get a feel for how things react.
> 
> ...


Somehow I saw "0" replies this AM, but now I see these. Thanks! That is honestly the first time I've ever seen the check valve inserted inside the cap. Mine can get clogged fairly easily as it is on the outside, but I will give it a try. I haven't ever seen those discard-a-stones, either. I'll tell ya, though, I've already (a few years ago & recently) tried all kinds of things, so I'm game! I broke down my largest tank, 75 gal, a few years ago when I thought we were about to move, so my tanks are small. I reckon I'll leave the Panda corydora's tank as is since it's been working, but have a separate 29 gal with pygmies, & I'd like to plant it with "real" plants. So, I probably don't need such a fancy set-up, but I do like it! I might try just 2 bottles with a 16 oz pop bottle I already have 2 holes in. That'll limit me, I realize, but I can possibly connect the 2 generator bottles with a single line (w/check valves IN each  & connect to the gas separator. I look forward to trying your schematic. It looks awesome! What do you use as diffuser?

Now something else occurred to me, concerning dispensing through the HOB filter. I have a boxful of those cheap sponge filter set-ups (& am using a few) with the double sponge intake tubes & single outlet. Of course, I don't have a clue about sponge filters in general, just happen to have some. What if... (please bear with me, I'm on the tip of the spectrum & ask dumb things often)... I turned one of those babies upside down in the tank & put the co2 outlet tube into the (now) intake tube, to be dispersed (now) out through the sponges? I'm sure there's a great reason why that won't work, so it's actually to my credit that I asked before trying it anyway.


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