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FAQs on Carbon Dioxide and Planted Tanks: Control & Delivery 

Related Articles:  Carbon dioxide and the planted freshwater aquarium by Neale Monks, CO2 Canopies

Related FAQs: CO2 & Planted Tanks 1CO2 & Planted Tanks 2, CO2 Canopies& FAQs on CO2 Planted Tanks: Rationale/Use, Sources, Yeast-Bottle Types, Compressed Gas Types, Measure, Dangers,


CO2 Diffuser Question   7/2/10
I have a 150 gallon 1/2" acrylic freshwater aquarium that I am converting to a planted tank. I have a co2 canister and a bubble counter but I know that wont be enough. I am having a hard time finding out 1) if I use the bubble counter, how many bubbles per sec do I need for such a large tank. I only have about 12 small plants so far and 2) If I use a diffuser, where can I find one the right size or style?
<Hello Lisa. The use of CO2 is tricky, and if you get it wrong you can stress or kill your livestock. I have to confess that apart from a period in the mid 80s, I haven't bothered with CO2 at all. So I'm definitely not an expert on the current state of the art! But what I would suggest is that you look into semi-automatic (~$100) and automatic (~$300) systems that have the timers and dosing mechanisms built-in. For the price these take a great deal of the hassle out of dosing CO2 safely. I'd also suggest you visit our friends over at TheKrib to see some of the useful summaries and discussions they have on CO2 and planted aquaria, here:
How much CO2 you need to use will depend on the pH you're after and the water's carbonate hardness, so there's no one perfect answer. You have to do some cross-checking yourself. As a general comment, I'd want to remind
you that CO2 is not essential, despite the marketing. You can create lovely planted tanks without CO2. Floating plants, hard water plants, and slow-growing plants are largely or completely indifferent to CO2 fertilisation because they either get their CO2 from the air (as with floating plants) or carbonate hardness (as with hard water plants) or grow so slowly that the ambient CO2 in your aquarium supplied by the fish will be sufficient for their needs. So before you spend time and money on this project, think about how important CO2 is for the types of plants you want to keep. If you're growing plants that need CO2 -- and to be fair, many do if supplied with bright lighting as well -- then opting for a semi-automatic system at least will be helpful. But if your plant selection doesn't need CO2, then you're off the hook! Cheers, Neale.>

Planted tank co2 question - turn off at night?   4/9/09
I looked through your site, thekrib.com and plantedtank.com, to find an answer to this question - should pressurized co2 be turned off when lights go off on a planted tank?
<No consensus on this. Arguments have been made both ways. On the one hand, plants don't use up CO2 at night and excess CO2 will simply bubble out into the air, but on the other, having a CO2 reserve in the water first thing in the morning means that plants can start photosynthesis more quickly. CO2 is rarely the make-or-break issue in planted aquaria (if the lights and substrate are acceptable, your plants will grow without CO2, though perhaps not as quickly). So you have scope to experiment without your aquarium
plants turning brown and dying. That said, it is usually recommended CO2 be left on 24 hours a day.>
It seems there is some debate on the subject. What are your thoughts?
<It's too complex a system to predict reliably. I'd always recommend experimentation here, observing plant growth while ensuring pH remains relatively stable. You don't want dramatic pH changes, though some slight change is almost inevitable as photosynthesis progresses during the day and CO2 concentration drops. This is normal, and fish and plants will tolerate it.>
I have plugged the solenoid into the power strip that is on 24/7, so it doesn't switch off. I measured my pH just before the lights went off at 8 p.m., and it was somewhere in the 6.8-7.0 range (hard to read the color
chart with API pH test kit). I then tested it just before the lights went on, and it was in the same range.
Specs if needed:
120g glass tank, 2 overflows (1.5") drilled through rear, to 40g sump through 2 filter socks.
Tube filter with bio media (Hiatt Tri-Pelletized Carbon) on power head, then up to tank with quiet one 4000. About 600 gph Returns are aimed downward, surface pretty still.
20lb co2 canister with needle valve, bubble counter, and back to intake of biotube filter (which doubles as a very efficient co2 reactor)
4x54 t5 HO (used to be 6x54, but shut off two bulbs, no difference in growth, definite difference in yearly energy cost)
soil is mix of ADA super soil, EcoComplete, pond soil (pure laterite) and silver sand
plants: HC, variety of swords, Riccia, Bacopa, Frogbit, water lettuce, wisteria, java fern, Val.s, crypts, Glossostigma, Ludwigia - everything doing well, growing well
<This is the main thing.>
fish: Plecos - 2 gold nuggets, queen arabesque, king tiger, goldie, leopard frog, red fin leopard; rainbows - 4 Irian Jaya, 7 turquoise, 2 millennium; 8 sterbai Cory; 4 SAE; 2 red tail Garra; 1 aeneus Cory; 4 Dennison's barbs; tinanti cichlid
ph 6.8-7.0
KH/Alk 70-80ppm
co2 in 14-16 range (if you can believe the Red Sea drop test kit)
amm 0
nitrite 0
nitrate 0-5ppm
PO4 .25ppm
Iron - Red Sea drop kit never registers
Dosing - Brightwell Labs Multi-Nutrient, 15 drops/day. Brightwell Ferrous and Ferric Iron Source, 15 drops/day
Water changes - about 30% every 10 days or so.
<All sounds great.>
Also, do you have any suggestions for DIY dosing? I've seen the PMDD stuff - do you know of anyone who makes it all ready to go (I don't want have to store a bunch of stuff around the house and make batches all the time - I've have three young kids and a curious dog).
<To be honest, no, I don't know much about DIY dosing. When I used CO2 back in the 80s, I found an automatic system more convenient, and would tend to recommend that today, despite the expense. The risks of overdosing, coupled with the reliability you want, e.g., when vacationing, makes the expense of
a properly constructed unit worthwhile, in my opinion. That said, do review the Krib articles, which are put together by expert aquarium plant keepers.
<Cheers, Neale.>

Adjusting CO2, pH, dKH, the "Shift" Key on Your Computer Keyboard - 7/16/08 Dear Crew, <Hello again!> First, I would like to say thank you to Benjamin. I have confirmed the bottle was indeed filled with co2;) <Welcome, and glad to hear it. My thanks to Bob for pointing out a simple test I overlooked/was ignorant of> I have a 250gal planted aquaria, heavily planted, with 30 cardinals, 2 Corydoras, 5swordfish, 3 algae eaters, 3botias,1 black ghost. All fishes seems to be doing fine- the swordfish just bred. Plant growth, however, has been slow. I'm experiencing difficulties in achieving the correct level of water parameters (ph; kH and co2 levels) currently my tank water has ph=8.5 and kH=11 I'm using sera test kit for testing the water kH and ph. I'm using well water that has ph=7.5 ; and kH=11. unfortunately, haven't found a gH test kits from my LFS, so I assume that the water has a high level of gH, since it shows marking on dry pipelines. <11 dKH also indicates high TDS> Recently I bought a CO2 unit from my LFS and it has been running for about a week. And made adjustment of about 5 bubbles per sec. and leaving it running throughout the night. Q: How come my ph doesn't show any changes? Should I pump up the CO2 rate? <I wouldn't> Is it because of the high kH? <This is buffering it, yes. Consider an acid buffer in your water changes> I've tried using RO water (with ph=7; kH=3)changes but after a few hours the ph and kH went back to 8.5ph and 11kh. <11 dKH in a 25o gallon tank is a lot of buffering capacity. Will take many water changes...also, do you have an sources of carbonate in your aquarium? Aragonite, limestone, etc?> Also, it will come to a time when I will have to make water changes that I don't want to keep buying RO water. <With your hard water, it may be necessary for you to purchase an RO unit to make your own- at a significant savings compared to purchasing the water> What should I do to make my life easier? <Use lower alkalinity in your water changes for a while, see if this helps. To make my life easier, please read our page on "How to Ask the WWM Crew a Question and do use punctuation, capitalization so that I don't have to type edit your email. These are all archived for posterity (and Google!) and it will speed the reply and posting- or prevent our ignoring it entirely- if you follow our guidelines.> many thanks, <No problem!> Hans. <Benjamin>

CO2 Injection in a Sump Return Pump, FW Planted...   6/11/08 Hi, WWM Crew, <Tom> Great website. A excellent resource. <Ave!> I have been in freshwater fish only aquariums for many years and then went to saltwater a couple of years ago. The saltwater tank has worked out fine. I am now planning to convert my saltwater tank to a freshwater planted aquarium with fish. In the process of setting up my saltwater tank I put a sump in. The sump is in the basement and I pump the water about twelve feet up to the tank in the living room. I really like how this has worked out and I would like to keep this set up for the planted tank. Great place to put heaters and other equipment. <Yes> I also plan to put in a fully automatic CO2 injection system. This is where my question comes in. Do you think I can inject the CO2 into the return pump from the sump? <Mmm, you could, but...> The return line from the sump pump goes up twelve feet to the 75 gallon tank in the living room. When the return line gets up to the tank I tee it and return the water to both sides of the tank. Would the CO2 get thoroughly mixed in the return water going back to the tank? <Carbon dioxide is actually quite water soluble... will go into solution most anywhere> I would have the CO2 controller in the living room and the PH probe in the tank. This would control the amount of CO2 going into the sump return pump. If you think this scenario will work, any thoughts on the best way to inject the CO2 in the sump pump? Thanks for your help. Have a great day. Tom <I still like to have a "visible" check on the injection... in addition to probes, what have you... Myself... I would opt to use a simple "bubble counter" and diffuser in some part of your basement sump... so you can visually check, see the propagation of gas... Bob Fenner>

Re: CO2 Injection in a Sump Return Pump -- 6/11/08 Thank you Bob for your response. It is appreciated. <Welcome Tom> I had planned on using a bubble counter like you said to have a visual picture of the CO2 going into the sump. I had planned to just take the hose from the bubble counter and put it into the inlet of my return pump. <Ahh!> Do you think going through a diffuser or reactor before going into my return pump would be better? <Mmm, not really... as prev. stated, the CO2 will reading solubilize> In your response (<Mmm, you could, but...>) I am not sure what you mean. Do you mean if I add the bubble counter and diffuser it would be OK. Or do you thing the whole idea is not the thing to do? Could you please elaborate on this. Thank you. Regards, Tom <Sorry for the lack of clarity. I was merely attempting to lead into my preference for providing a visual cue... your in-line bubble counter will accomplish this just as well. Cheers, BobF>

Plant CO2 questions -- 1/2/08 Hello. <Katherine> I was wondering what the average bubble rate should be for a co2 system to be beneficial to plants. <Mmm, depends... on how much plant life, metabolic rate, lighting... other aspects of water quality, particularly nutrient availability and alkaline reserve...> I have a 55 gallon tank and want to add CO2 to it. <Is a worthwhile project> However I heard that letting the CO2 run 24 hours isn't the greatest thing ever. <Correct. Likely best to use a controller... or to have a timer turn off during "dark" hours> If I bought two Hagen co2 systems, which only effect 40 gallons total, would it still be a problem to let that run overnight? thanks. <Depends... FWIW I would read a bit more re this use before investing... Some definite potential downsides... Can be over- mis-used... Do read here: http://wetwebmedia.com/PlantedTksSubWebIndex/co2agfaqs.htm and on the Aquatic Gardener's Association site re. Bob Fenner>

Planted tank CO2 flow rate - 05/05/2006 Hi WWM crew, <Nick> Firstly, love the site and a huge thank you! <Welcome> I'm about to set up a planted tank and am considering using a Clippard EC-2M-12-L electronic valve instead of the more typical needle valve (e.g. Clippard MNV-4K2) and solenoid configuration. http://www.clippard.com/store/byo_electronic/byo_mouse_valves.asp I need to determine whether the flow rate of this valve is adequate to supply the CO2 needs of a 4 ft planted tank. <From their site... yes, they have many such valves> From the data sheets the Clippard MNV-4K2 needle valve flows a maximum of 5 SCFM, whilst a Clippard EC-2M-12-L flows a fixed 0.5 SCFM. To me the flow of 0.5 SCFM seems to be adequate, especially in terms of the usually quoted 1-5 bubbles per second flow rate for a planted tank. <Yes... much more than adequate... I would actually rig this system up, try counting the bubbles produced per your setting... to see if this is going to be too much. I would measure the resultant drop in pH here. Bob Fenner> Thanks. Nick Daglis.

CO2 Regulator - Milwaukee vs. JBJ? - 03/31/2005 I am interested in starting a freshwater planted tank using CO2 fertilization, but am in need of some help in choosing a good CO2 regulator. I've been looking at the regulators by JBJ and Milwaukee, but both seem to have a downfall. The JBJ has a fixed working pressure that is factory set and non-adjustable, and the Milwaukee does not include a check valve in its attached bubble counter. <Downfalls, indeed. I would think that the Milwaukee would be easier to manipulate to your needs....> On at least two websites I've seen the Milwaukee regulator for sale, but adapted to include a bubble counter with check valve. Most recently, on Aquariumplant.com, I found what they refer to as a "Top Gun" CO2 regulator. By calling this company I learned that this is actually a Milwaukee regulator adapted to include a bubble counter with check valve. <Strikes me that this is the better option.> This leads me to wonder if I can just buy a Milwaukee regulator as it is typically sold and adapt it myself.  <Probably.> In other words, does anyone know if there is a bubble counter with check valve that can be purchased to replace the bubble counter without check valve that the regulator comes with?  <Mm, I don't see why not.... I don't know of any specific details to give you, as I have only limited experience with pressurized CO2 systems.> I know the JBJ bubble counter with check valve is sold separately, but I don't know if it would be compatible with the Milwaukee regulator.  <I also do not know.... You could contact the manufacturers, but I'm not certain they'd be inclined to give advice regarding modding their products to work with competition's products.> Any additional advice you can provide regarding CO2 regulators would be greatly appreciated. <My best advice to you is to hop on a planted tank forum, such as the all wet thumbs forum at http://www.aquabotanic.com , and find out from folks who have done exactly what you are looking to do. I apologize for not having all the answers for yah, but I'm sure someone there will.> Thanks!  <You betcha! Wishing you and your plant tank endeavor well, -Sabrina>

CO2 plant tank questions 7/29/04  Hello all, I last contacted you last fall when I was setting up my 50 gallon planted tank and you all were exceptionally helpful for which I'm eternally grateful.  I'm now thinking about taking the plunge/dive/leap into CO2 and have a couple of questions for ya, if you don't mind. I have a "reasonable" collection of plants (a couple Amazon swords, some Ludwigia, a couple of crypts, a couple of Vallisneria, and some newly planted wisteria and moneywort). Fish-wise, I have 9 true SAE's, a somewhat ornery krib, 4 white clouds, 3 Cory's, 3 Oto's, and about 6 Amano shrimp.  Lighting is ~144w, half full-spectrum and half actinic (I believe, I haven't looked back since installing them last fall).  pH is ~7.4, KH about 2-3, GH? (my home has a water softener installed and my test kit never seems to give an understandable reading).  I have a Magnum 250 canister filter that I normally keep filled with activated carbon.  I'd like to do a pressurized CO2 setup with a 5# tank, regulator, needle valve, reactor/diffuser, bubble counter, etc. Mainly to improve my plant growth. 1.  Any way you think I could run the CO2 into the canister to use that instead of a separate reactor?  < Sure , but the bacteria in the filter will utilize the CO2 just like a plant so you will have to measure your CO2 levels for awhile until you get the readings you want.> 2. Someone is selling a canister/regulator on eBay - I *think* it would work but I'm a little wary of the "fixed pressure" he mentions in the description - is this what I want, assuming that I use a needle valve to control the flow? < Looks like this will work just fine.> The description reads: "Aqualine Buschke CO2 Regulator. The regulator unit is completely chrome plated and has a fixed working pressure of 1.5 bar, a needle-valve for fine adjustments, and two pressure gages showing both bottle and working pressure. The regulator fits every industry standard CO2 bottle with an external valve. 5 lbs co2 tank with brass valve The Cylinder is less than five months old for CO2 use in aquariums, beverage dispensing and paintball. A CO2 valve is included with a standard fitting for easy connection to all regulators. I bought these items new about six months ago to help with my planted aquarium. The increase in plant growth was incredible. Unfortunately a house move has forced me to sell the aquarium and all the accessories." 3.  My wife is a little concerned about having a CO2 tank in our dining room (leaks, explosions, torpedo's, etc).  I assume that treating these things with respect (including strapping them upright) and monitoring for leaks will drastically reduce those risks - am I correct? < CO2 is not flammable so as long as the tank is not ruptured or the top is knocked off you should be fine. A fire will increase the pressure inside the tank and a slow leak is no big deal.-Chuck> Thanks VERY much in advance for any advice you can provide.

Installation questions re CO2 for freshwater I'm installing a CO2 reactor for a freshwater planted tank.  Please see pictures attached.  Does it look like I installed this right? <Yes, does so to me> It's a JBJ Solenoid Regulator with a JBJ check valve/bubble counter.  I'm not sure how the bubble counter/check valve works.  Is that supposed to fill up with water? <Has to be filled with liquid to show passing of bubbles> I can regulate the carbon dioxide flow by watching the output in the vortex chamber when the pump is off.  How many bubbles per minute should it be? <You'll need to experiment with some aspect, likely pH of your system... I would start off with 30 bubbles per minute (one every two seconds) during the light hours (during photosynthesis) and see how this does for your plants, altering the system pH, and "turn it up" a few weeks from now if you find you want more growth, can support the addition of carbonic acid> What pressure readings should be on the gauge?  As long as it's not in the red, it's OK? <Mmm, strictly speaking, yes... on the main/supply side the tank will read several hundred psi when the tank is full, cranked all the way open (it can read just a few pounds to tens of pounds though to supply the "needle valve"... and this should read a few pounds psi... just enough to "push" the CO2 through the bubble counter, into the diffuser. Bob Fenner>

- CO2 Offline - I have a Milwaukee regulator and SMS 122 controller combo with my 125 gal planted community tank. Looks like the solenoid has gone bad or the connection from the controller has mysteriously stopped working.  Plenty of CO2 in the tank and both gauges show pressure.  Controller blinking signal to open solenoid. My pH has shot up to 7.6 from 7.0.  I keep my KH at 5 with Seachem Alkaline buffer, so I assume the pH will naturally drift towards 7.8. <Likely.> I have a variety of community fish that includes neon tetras, gold nugget Pleco, German blue rams, Juli Corys. How long will these fish be ok at the higher pH? <Hmm... well obviously not forever, but they should be fine for a little while - week or two.> Are there any emergency steps I should take? <For starters, I wouldn't add any more buffer... you might also try to add CO2 for the moment via a DIY yeast reactor.> I think that it will be difficult to bring the pH down and maintain it with Seachem Acid buffer. <Still, might be worth the effort in the interim.> The Milwaukee unit has the regulator, solenoid, and needle valve all together and I don't know if I could take them apart if I wanted to. <Bummer... you might want to procure a different unit that separates the controller from the solenoid/valve assembly - would give you more options in a situation like this.> I hate to have to buy another regulator/solenoid/needle valve while the original is fixed (and then have an extra), it's only 3 months old. <Still, the all-in-one construction is now a pain in your but, no?> Any thoughts/suggestions will be appreciated.  John <Cheers, J -- >

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