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FAQs on Carbon Dioxide and Planted Tanks: Measure

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, Control/Delivery, Dangers,


Pressurized CO2 System.   12/16/11
Hi Crew,
I have recently converted one of my tanks which is a 6x2x2 from marine to planted with discus fish. This is my first venture into planted and I have set the system up after much reading. I opted for a pressurized CO2 system with control via a JBL computer that has a temperature probe and ph meter as although expensive seems the correct option for optimum CO2 addition whilst making things easy once set up.  I use a RO / tap water mix and set the JBL up as instructed. Everything seems fine and my plants are growing really well and fish look good with even one pair of discus spawning although I felt some of the discus were breathing slightly heavier than I would expect. My KH was 5.5 and temperature is 29°C so the JBL has injected CO2 to hit a target 7ph. This has all been running fine for a good few weeks. The thing I get confused with is when I use my API fresh water test kit the ph is always different to the JBL reading and normally measures at around 8.4ph. I even bought another API test kit to see if this would give the same result which it did. Which system should I take as correct the JBL or API?
<Hello Gary. The reality is you can't trust either of them. Do be aware that scientific-grade test kits are either expensive, require serious practical chemistry expertise, or both. As aquarists we use and rely upon test kits that don't have anything like the accuracy or reliability we'd expect medics, vets, or biochemists to be satisfied with. This isn't to say test kits are useless, but that their results should be take for what they are: approximations. Now, the proof of the pudding is always in the tasting. If your plants are thriving you have at least enough CO2 for them, but if the fish are breathing heavily -- and the tank isn't overstocked -- then something is lowering oxygen concentration, and that might be either temperature or CO2 fertilisation (and the fact we usually minimise water current, turnover and surface agitation when fertilising with CO2). So, the best thing would be to conservatively adjust accordingly. Lower the temperature to 28 C, which is fine for Discus, and see if that helps. Look to see if you have water circulation set just a bit too low, a common temptation when we prioritise plants above the fish. Do recall that "Amano" tanks usually have to be lightly stocked with very small fish because circulating the water sufficiently well for larger fish means we'd drive off the CO2 at air/water interface. Try lowering the amount of CO2 a tad, perhaps by 20%, and see if you can keep the same sort of plant growth without raising CO2 concentration above that the fish appreciate. Finally, do realise that pH varies a lot in brightly lit aquaria, regardless of what CO2 fertilisation might be expected to do. This is especially the case if CO2 is the thing lowering the pH. When the plants use up CO2 during the day, pH will rise, and when they stop using up the CO2 by night, pH drops down again. If you have a 50/50 mix of RO water with hard tap water, chances are some of the CO2 is reacting with carbonate or bicarbonate salts, and that adds a whole other level of complexity with pH variations between water changes as well. Ideally, you'd go 100% RO water mixed with Discus Buffer, so that the carbonate hardness side of the equation could be minimised. But if the fish are basically happy and the plants are thriving, I wouldn't worry too much. Perhaps try and deal with the heavy breathing problem, test the pH a few times across the day, and see if you can establish what's going on in your aquarium. Hope this helps, Neale.>

How to differentiate CO2 from O2? - 7/10/08 dear sir/madam, <Hello! Benjamin here> I have a 250 gal planted tank, and after reading and doing some DIY yeast CO2 stuff, I decided to buy the real system. The only problem is, how can you tell if the gas inside the bottle is really CO2? Is there any way to test it? <There isn't a way a hobbyist can easily assay the purity of the gasses in the cylinder, however, purchasing your cylinder from a reputable source and having it refilled properly will ensure you have CO2> thank you. <Welcome. Benjamin><<Mmm, could bubble a bit through some freshwater... Carbon dioxide is much more water soluble... and will drop the pH quickly... You won't be making other gasses here though. RMF>>

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 levels I have purchased a CO2 system and LaMotte test kit for my Freshwater Aquarium . Is there a recommended level for CO2 for a planted tank that I could use for a guide line ? Would appreciate your assistance . Dieter Cordes Leesburg , Florida <Hi Dieter, aquabotanic.com and www.thekrib.com have a lot of good information on this topic, check out the links below for more information.  Best Regards, Gage http://www.aquabotanic.com/charts.htm http://www.thekrib.com/Plants/CO2/  >

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