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Hi all, We have CO2 monitors <"in the teaching lab">. They rarely get to 1000 ppm, but it is probably better ventilated than an average house. cheers Darrel

Hi all, I'm going to guess that the CO2 concentration is higher than the <"theoretical value derived from Henry's Law">. I know with wastewater treatment (and aquaculture) one of the issues is getting the CO2 to outgas efficiently...

Hi all, I'm <"not a CO2 user personally">, but I know a bit about the <"practical difficulties of pH measurement"> and I wouldn't rely on a pH meter, but I would be happier to use a drop checker. <"Almost 0.6 ppm now">, due to the rise in <"atmospheric CO2 levels">. It <"comes from"> the work...

Hi all, It is quite a problematic area, even if you have some scientific background. The drop checker works because there is an experimentally derived relationship between carbonate hardness (dKH or alkalinity) and pH. The design of the drop checker, with an air gap, means that only gases (and...

Hi all, That was <"Diana Walstad's original premise">, and part of the reason for the (mid photoperiod) lighting siesta. Organic matter in the garden soil would be aerobically decomposed, liberating CO2. and the lack of water movement would then help retain the CO2 in the water column. I'll be...

Hi all, There is a <"definite suggestion"> that citric acid (HOC(CO2H)(CH2CO2H)2 (or C6H8O7)) aids plant growth. Now that is interesting, freshwater copepods are usually difficult to culture (in reasonable amounts)...

Hi all, Honestly, <"don't even think about it"> & <"Exploring yeast as shrimp and plant food"> In a planted freshwater tank <"that is what the plants do">. cheers Darrel

Hi all, Cherry Shrimps are fine in hard, alkaline water, it is <"soft water that is unsuitable for them">. No, not really. You can't really <"add things to soften the water">, you can add an acid to reduce alkalinity, but it is a <"pointless exercise">. My opinion is you are best using the...

Hi all, We have a thread for you <"Updating an old aquarium, Juwel Rekord 72, and other ramblings">. You don't need CO2, a lot of people don't use it. Have a look at <"Cryptocoryne Parva Carpet"> & <"What is the “Duckweed Index” all about?">, it talks about the "aerial advantage" that...

Hi all, I think they measure alkalinity, it is back to @Andy Pierce's post <"earlier in the thread">. They are "universal" because the paper was prepared with a range of pH indicators, that have different pH responses <"pH Paper and other Test Strips | Fisher Scientific">. If you have an...

Hi all, Thank you. I will eventually get there. cheers Darrel

Hi all, I just couldn't run CO2. I'd never recover from that. cheers Darrel

Hi all, One more question. Is the H2CO3 going to disassociate into a proton (H+) and bicarbonate ion (HCO3-)? And the pH fall is actually because of the addition of the H+ ion? and both it and the HCO3- ion will contribute to the conductivity (because they are ions)? cheers Darrel

Hi all, Edited - <"C02 injection with already low ph"> Same for me, it hadn't really occurred to me. Now @MichaelJ has mentioned it, he is obviously right. A thought occurs this also allows you to <"sell the same reagents"> as two "different" test kits, for "dKH" and "pH"...

Hi all, Thank you, <"I will eventually get there">. I'll go back and edit that bit. Although this was ten years ago <"TDS vs hardness">, so there maybe no hope for me. In best <"Seachem fashion">, I'm now going to throw in a <"total red herring"> and say that I'm very good <"at identifying...

Hi all, At least I got the broad brush bit right. Please correct. As <"you've already found">, I'm not a chemist and <"I really struggle with this">, what is important is we get the science right and that I can refer back to this the next time I'm hopelessly confused. That was partially why I...

Hi all, That works, it is <"add a neutral salt"> (usually NaCl) method. This is because pH meters are a <"special type of conductivity meter"> and the salt addition raises the amount of ions in solution (Na+ and Cl-), but these cancel out in terms of pH, which is why it is a "neutral salt"...

Hi all, That is just because of inorganic chemistry, there is a <"CO2 ~ dKH ~ pH equilibrium"> and if you have 2 dKH you need more than atmospheric levels of CO2 to get to pH 6.4. That is why @Wookii was interested in if it was recently drawn tap water, this would be likely to have higher...

Hi all, That doesn't look too bad. They can gulp air, but you'll need some-one with more experience of CO2 to advise you. Can you get a water report from your water company? The tap water will be hard and relatively nutrient rich. It is going to supply most of the essential plant nutrients...

Hi all, Welcome to UKAPS, It should be fine, there <"isn't really a cycle">, particularly in planted tanks. Is there any livestock in the tank? And can we have a picture? Assuming you don't have any livestock? Then you can add as much CO2 as you like and it will help the plants grow as long...

Hi all, @Mick.Dk <"discusses this"> when he is talking about looking after the Tropica stand at Aquarium conventions etc. There is some discussion of this in <"Is CO2 really worth it??">. cheers Darrel

Hi all, As long term forum members will know I'm not, nor ever likely to be, <"a CO2 user">, so I have no practical experience, but I am pretty familiar with <"pH meters and pH measurement">. @Andy Pierce 's point would be exactly the one I'd make. A drop checker, <"with 4 dKH solution"> and...

Hi all, I'm <"not a CO2 user">, but I wouldn't be too concerned. Have a look at @Roland 's tank and water parameters <"Soft water tank"> & <"What's the deal with kH/Alkalinity?">. In terms of your livestock, if you don't keep <"Lake Tanganyikan fish">? I think <"the same applies">. The pH...

Hi all, Yes, agreed I don't think "bioassay organism" is ever a great thing to be, I'd put it up there with "potential organ donor" & "crash test dummy". Having said that I only originally had one Seminole Ramshorn (Planorbella duryi) snail (in ~2008) and these are all its descendents, so...

Hi all, That is about <"where mine end up">. At the moment I have a fewer large ones, but the softer rainwater in the winter will probably see them off, unless I add <"enough tap water"> to keep them going. It works <"surprisingly well"> as a bioassay. cheers Darrel

Hi all, Well at least <"I got that bit right">. cheers Darrel

Hi all, I also have friend who is interested in the outcome of this one. Cheers Darrel

Hi all, This is when a <"little learning is a dangerous thing">, and I patently need a bit more. I just wish my <"inorganic chemistry was better">. I'm not an added CO2 user, and this was all new to me when I joined UKAPS. The only problem is that its fifteen years on and I still don't know...

Hi all, You can. If you don't like playing with small weights you can use serial dilution to get to the 4dKH solution. Sodium bicarbonate is a <"cheap chemical to buy">. cheers Darrel

Hi all, OK. I've never kept Nerites, and the only hard water Mollusc I've tried were <"Anentome helene">, but I would keep an eye on the oldest shell whorls, that is where signs of attrition (probably initially loss of pigment) will occur first. My Ramshorns <"look better (and bigger)"> than...

Hi all, I think you are good. I'd imagine the Rabbit Snail (Tylomelania sp.) is the best indicator. They come <"from Lake Poso etc">. which have relatively soft, but alkaline, water and if it doesn't show shell attrition after five years? I think you are pretty safe. cheers Darrel

Hi all, That maybe the bubble nuclei forming where there are rough sections in the Nerite's shell - <"https://royalsocietypublishing.org/doi/10.1098/rsos.230376"> or they may just <"be being "trapped"> by the rougher sections of shell. I'm guessing that that is actually the <"start of shell...

Hi all, @hax47 good post. I think a larger gas exchange surface area is beneficial in a low tech for both carbon dioxide (CO2) and oxygen (O) exchange. I like <"a venturi on a powerhead etc">, because I'm not too bothered about CO2 concentration, but I want there always to be <"a lot of...

Hi all, Water Lettuce (Pistia stratiotes) would definitely be my <"floater of choice">, if it was "leaf green" rather <"than silvery">. I need a <"green plant for the Duckweed Index to work">, but I still have Pistia in all the tanks, partially because <"of its great roots">. cheers Darrel

Hi all, I'm not a CO2 user personally, but the reason for the solution of known dKH in the drop checker is because of the known relationship between CO2 content and pH change. <"CO2 Measurement Using A Drop Checker"> It does, the <"protonation state"> of the narrow range pH indicator...

Hi all, I've checked and you are right, there is <"no direct effect on pH of elevated DO levels">. I should have realised that from high tech aquariums, (with added CO2), if oxygen affected the pH level you would need to continually add more CO2 as the oxygen level (from photosynthesis) rose...

Hi all, I'll be honest, I don't actually know, I know you <"get these extreme diel pH swings"> in vegetated water, but I don't know how much is a CO2 effect and how much an oxygen one*. I'll try and find a reference that quantifies the effects of oxygen accumulation on pH. I'm pretty sure...

Hi all, We have a sticky <"Some handy facts about water">, but 1dKH = 21.8 ppm HCO3-. You are in for a treat, all explained here: <"Spotless water...help me understand"> details in Larry Frank's Krib article <"Water Hardness">, abstacted below. cheers Darrel

Hi all, This is an interesting experiment and you have ended up pretty close to the theoretical equilibrium values. I think you might have to take <"oxygen saturation into account as well">. If you get above 100% oxygen saturation it will <"cause the pH to rise">. You might also have more...

Hi all, @Andy Pierce , I think that is this bit <"Carbon Dioxide as an Acid">? I think this is the best we've got <"Estimating CO2 injection rates in ml per minute">? Again I have dim recollections that we might have a better, more recent, thread, but I can't find it. cheers Darrel

Hi all, We don't actually know where the 3 ppm CO2 figure comes from. Cheers Darrel

Hi all, There is another thread somewhere that talks about CO2 disassociation. I'll see if I can find it Cheers Darrel

Hi all, We have <"a thread.....">. Cheers Darrel

Hi all, That's why I said "almost". @Hufsa had <"manganese (Mn) deficiency">, as a result of their incredibly pure tap water in the far frozen north. Cheers Darrel

Hi all, The aerial advantage was the main reason for using a floating plant for the "Duckweed Index". Once you've taken CO2 (and light) out of the equation, that only leaves the mineral nutrients. You can divide the mineral nutrients into those that are mobile within the plant (the majority)...

Hi all, So you need to convert the 0.04 percent atmospheric CO2 into mg/L, and mg/L and ppm are equivalent*. <"Global Monitoring Laboratory - Carbon Cycle Greenhouse Gases"> This means that we have about 420 ppm CO2 in the atmosphere and over 10x as much as you are adding. This is described...

Hi all, I've been wondering as well. I'll try emailing him. cheers Darrel

Hi all, That sounds a plan. I'm <"not a CO2 user">, but if I was? <"I would use drop checker">, purely because it removes a lot of guesswork. Cheers Darrel

Hi all, Because you live in Cambridgeshire your tap water is going to have dGH (General hardness) and dKH (Carbonate hardness, measured as alkalinity) <"values of ~17 dGH & 17 dKH"> and the pH will be ~ pH 8. <"This thread"> gives the derivation of dGH & dKH and also explains why their ratio...

Hi all, Softer (less alkaline) water now? cheers Darrel

Hi all, It's sort of halfway there. The atmospheric CO2 level controls the amount of (D)TIC (Dissolved(Total) Inorganic Carbon) in solution and the pH value is dependent upon the <"ratio of HCO3- and CO2"> (from the 0.15% <"dissolved as H2CO3"> which disassociated into a proton (H+) and...

Hi all, Same for me (both growth and age thing). I actively want plants <"that will grow slowly">. I like a fast growing plant purely as a nutrient sponge (<"belt and braces">) should any <"untoward event occur">. I've got around the potential "lack of CO2" issue with <"a floating plant">...

Hi all, Just @Mick.Dk 's <"post">. I would assume that Tropica came upon that formula via trial and error. Mick had a slightly strange position on the forum, where he made no secret of the fact that <"he worked for Tropica">, but also that while he was on the forum as a representative for...

Hi all, Personally I'm not a CO2 user <"CO2 Disaster">, but it definitely would give the plant a short term CO2 "burst". It is actually where <"Takashi Amano started">. This is from @Mick.Dk, who worked for <"Tropica">, and he even gives a dosing amount "Dose one cup (app. 2 1/2 dl) to 100 l...

Hi all, <"Sparkling bottled water"> would <"work">. Carbonated drinks contain a <"huge amount of dissolved CO2">. I think @Oldguy still does this? cheers Darrel

Hi all, It is slightly more, as @LightingBamboozled suggests, and the three important bits are: The <"air gap"> between the tank water and drop checker fluid, this means that only the CO2 that diffuses across the gap effects the <"pH of the drop checker fluid">. The <"4 dKH fluid"> in the...

Hi all, I think they are, but I'll need to find the paper and check. Cheers Darrel

Hi all, The main Amazon river (Solimões) is carbonate buffered to some degree, particularly above its confluence with the Rio Negro (which isn't) it is just because its headwater arise in the Andes and streams from the Andes piedmont have a greater sediment load (they are "white water" rivers)...

Hi all, It will be (tri)sodium citrate (Na3C6H5O7.2H2O). It is one of the <"products of the reaction"> (along with CO2). It is a <"soluble salt">, so it should dissolve in a <"reasonable amount of warm water">. Cheers Darrel

Hi all, I'd actually say that is the aim of all amphibious plants, to <"get above the water's surface"> and get access to atmospheric gases and pollinating insects. This why you get <"obvious zonation"> in turloughs...

Hi all, Yes, agreed. I've had Echinodorus bleheri, Anubias barteri, Cryptocoryne spp., <"Bolbitis heudelotii"> & Hygrophila corymbosa plants that have spent at least the last ten years submerged, and probably a lot longer. I'm guessing that is partially why these sorts of plants persist in the...

Hi all, No, I think it does make sense and that they are right. I think it is much simpler than that, they weren't growing in rivers (or not permanently), they are plants that are perfectly adapted to <"atmospheric CO2 levels">. It is the <"Murdannia keisak"> or <"wet paddy rice"> scenario...

Hi all, Thank-you, it did make sense as "oxygen" the first time, but that is unambiguous. I understand that, it isn't <"what I'm interested in">, but I have an <"understanding wife"> and she doesn't insist on <"aesthetic quality"> (and the tanks are in the kitchen). We have plenty of members...

Hi all, No, <"UKAPS"> (and the <"waste water industry">) got <"there first">. It is definitely the safest method of sterilising plants. cheers Darrel

Hi all, Should that be three mg / L CO2? or are you saying that you aim for more than three mg / L dissolved oxygen, even though your fish will survive at that level? cheers Darrel

Hi all, It is still "as clear as mud" unfortunately, but I'm reverting to "unreasonable" This is from "Hasler CT, Butman D, Jeffrey JD, Suski CD. (2016) Freshwater biota and rising pCO2? Ecol Lett. 19(1) pp 98-108. <"https://onlinelibrary.wiley.com/doi/10.1111/ele.12549">. Which at least...

Hi all, The conversion chart for partial pressure. and here are some figures*: and a useful graph So it looks like they aren't as unreasonable as values as I thought they were, but I'm still not entirely convinced that all the values are looking at dissolved CO2. 1 kPa ≈ 10,000 μatm ~1 mg /...

Hi all, They definitely aren't right. edit: they <"maybe right"> It is back to the <"bouncy castle"> analogy. Although CO2 is <"incredibly soluble">, at those sorts of CO2 levels you are literally going to have to be pumping CO2 in, because it will be lost at a great rate at the gas...

Hi all, I think he did, we have a thread somewhere, but <"not this one">. You can't search for "CO2" and "Amano" isn't a very useful search term, so it may take a while to find, cheers Darrel

Hi all, Former member @Marcel G <"tried 15ppm CO2">, I'll see if I <"can find the thread"> elsewhere. Here <"Akvaristika">, in English: <"Aquarium"> Same for me, I'm never going to be a CO2 user. I would say that the main advantage of adding CO2 is that it allows you to grow plants that aren't...

Hi all, I'm busy today, but when I've got time I'll see what I can find in the scientific literature. I think it is just a slightly different chart to the one @_Maq_ posted. cheers Darrel

Hi all, Something is definitely wrong there. I've never seen a <"theoretical dKH ~ CO2 ~ pH chart"> that goes below pH6, but I can't see the chart will work at below the level of dKH that would raise the <"pH to the equilibrium value">. If you look at the Rio Roseira, the conductivity was 16...

Hi all, I'd guess they probably did, because it says "CO2 calculated." and some of those are pretty unlikely values. It might have been by titration, but you would still have to assume all the the acidity was from dissolved CO2. You would need to use a specialist dissolved CO2 meter and probe...

Hi all, I think a lot of it depends on the fish. I'm going to guess that 30 ppm CO2 would quickly kill off most <"rheophilic fish"> and <"Tanganyikan cichlids">. This is an Arctic Charr reference <"https://www.grocentre.is/static/gro/publication/261/document/safina13prf.pdf"> and this a General...

Hi all, Can you get figures from your water supplier? You are likely to have <"softer water than most of us in S. England">, because of the Weald, but your pH looks a bit low. cheers Darrel

Hi all, A bit of both I'd guess, the electrode (<"ISFET etc">) type is probably going to make most difference. Problems are most likely to occur in the pH 6.5 to pH 7.5 range (around neutral), particularly in solution with low electrical conductivity. As long as people recognise that you...

Hi all, They work by swapping an internal potassium (K+) ion for an external proton (H+ ion) in the water. Because <"pH is a measure"> of the relative ratio of H+ and OH- ions (I'm going to ignore the <"log 10 scale, the hydronium ion and the self-ionization of water">) then the more...

Hi all, Unfortunately they need calibrating every time you switch them on, and you are even meant to re calibrate them every so often when you are doing a continuous long run of samples. You really need two point calibration (pH 7 & pH 4 or pH 10) as well, dependent on what you think the pH of...

Hi all, Approximately how much is "spending out", they get pretty pricey, pretty quickly. If you want an a <"reasonably accurate one"> you are into the £ hundreds and if I was going to buy one (rather than <"just using the ones at work">) <"I'd get a solid state ISFET meter">. There are also...

Hi all, We got the CO2 monitor up to 2000 ppm by breathing into, I think the highest it has been otherwise is about 1200 ppm with bunsen burners on. The lowest level is <"higher than that now">. This is today's graph. cheers Darrel

Hi all, True, but I'm not sure it is a workable idea. I'll be honest, for me I'm not too worried about submerged CO2 levels. I always have floating (and sometimes emergent) plants and <"they have access to ~420 ppm CO2">. <"Dissolved oxygen does interest me">, and I'm always willing to...

Hi all, We have a thread that may be of interest: <"Determination of CO2 in combination with an aquasoil">. We <"have them in the lab.">, if you get to 2000 ppm CO2 they sound an alarm and turn the gas and electric off. cheers Darrel

Hi all, Yes, that's it, it is the George and Karla Booth reference linked in the earlier post, by @xim Cheers Darrel

Hi all, That is the one, CO2 is a very minor component of the atmosphere, but <"incredibly soluble">. There has been a lot of discussion as to where the 3 ppm figure comes from, because <"theoretically it is only about 0.6 ppm">. cheers Darrel

Hi all, I'm guessing that is probably the reason for Dennis Wong's comment, it is the bubbles of CO2, in contact with the leaf surface, that maximise CO2 uptake. I think that is right as well. There are plenty of <"pictures of "pearling"> where the bubbles have definitely not come from the...

Hi all, I'm not entirely sure. Once you have more than ~2dKH (~ 44 mg / L HCO3-) a one unit in pH fall indicates about 30 ppm CO2, despite the base 10 logarithmic nature of the pH scale. @Manuel Arias gives the full explanation in <"Drop checker color relation to KH question">. I'm guessing...

Hi all, It shouldn't matter, it is a weak acid but you need to have enough <"bromothymol blue"> to be able to see the pH colour change. cheers Darrel

Hi all, I would, 2000ppm is <"getting towards the limit for healthy living">. It will definitely cause drowsiness, and above 2000ppm aerial CO2 you get Probably a silly question, but can you just open a window? cheers Darrel

Hi all, That is true generally, because it is back to the <"Bronsted Lowry definition of acids">, that they are proton (H+ ion) donors. <"It is that one">, @Manuel Arias, gives the <"chemistry in this post">. In <"this specific case">, when we add CO2, we are simulating an <"atmosphere richer...

Hi all, That is it. Cheers Darrel

Hi all, When you add CO2, you change the equilibrium point of the CO2 - HCO3- - pH relationship, so the very useful curves that @jaypeecee showed aren't relevant, because you have more DIC in total. How much of that Dissolved Inorganic Carbon is in the form of H2CO3- is given by the pH value...

Hi all, Yes, it is a dynamic equilibrium, so it happens fairly quickly. The actual rate of reaction will depend upon the solubility of the carbonate source, so a really hard marble (metamorphic Ca CO3) will take longer to go into solution than an aragonite CaCO3 source, like a cuttle "bone'...

Hi all, I'm a <"mechanical, analogue timer fan as well">. You can buy better quality ones for use with Metal Halide lamps etc. I'm still <"using these ones"> bought in 2008, although I no longer use the HPS grow lamps. cheers Darrel

Hi all, I should have put the graphic and calculation for this: If we take 500 micromol. (as the point at which adding more CO2 doesn't increase plant growth) that can be converted to ppm CO2 using the RMM of CO2, which is equal to 44 (12 + (2*16)). A molar solution of CO2 is (a theoretical)...

Hi all, Welcome to UKAPS. There are lots of <"scientific references"> available via "Google Scholar", this one would be a good starting point (and should be open access?): "Sand-Jensen, K., Riis, T., & Martinsen, K. T. (2022). <"Photosynthesis, growth, and distribution of plants in lowland...

Hi all, I think they will <"buffer the water"> to some degree. If you don't have many plants it will limit the pH variation upwards, just because you will never have that much "excess" oxygen*. Point taken, I have had some tanks <"where snails won't survive">, and <"black-water is a special...

H all, That is the real issue, as you approach pure H2O pH becomes less and less meaningful as a parameter and very small additions of acids <"and bases"> cause <"huge variations in pH">. I use <"shell attrition"> in my Ramshorn snails as a rough proxy for dKH (and therefore indirectly pH)...

Hi all, Same for me for our tap water, straight from a limestone aquifer and about 17 dKH and 17 dGH. Something is still a bit strange, because that <"isn't much calcium (Ca)">. The magnesium (Mg) content is for <"geological reasons">. Yes. cheers Darrel

Hi all, With the usual disclaimer that I'm not a CO2 user and I never will be, but I do know a reasonable amount about pH measurement via my "day job". That would be <"worry straight away">. Most of the probes work by exchanging potassium (K+) ions from <"their internal supply"> for protons...

Hi all, That is the NaOH addition by your city, it is designed to stop copper (Cu) and lead (Pb) (from old pipes) <"going into solution"> in your, naturally soft, water. I'd guess that is more "Equilibrium" than you need. Have a look at <"James's Planted Tank"> for some DIY options. Plants...