Midas Posted June 12, 2002 Report Share Posted June 12, 2002 Does anyone use the correlation between KH and pH as an estimate of CO2 concentration (as posted on the krib website) and if so does it really work? It sounds feasible to me under normal water chemistry situations. http://www.thekrib.com/Plants/CO2/kh-ph-co2-chart.html Quote Link to comment Share on other sites More sharing options...
Warren Posted June 12, 2002 Report Share Posted June 12, 2002 This method works fine if you have really good test kits that can measure accurately in the 2-4dH range. Most test kits (all I've tried) only give 1dH steps of accuracy. This allows you to only approximate the CO2 and it could be out by as much as ±50%. I've found the best method is to add enough CO2 to make the plants happy and no more. If in doubt, err on the low side until you are sure. I have a CO2 test kit. I haven't checked to see how it works. Many test kits rely on the pH and KH being between certain values to give correct results. The one I use is a Tetra brand. It seems to go ok and tells me I have between 10-20ppm CO2. Its not very accurate, but indicates its within the right amount. Quote Link to comment Share on other sites More sharing options...
Midas Posted June 12, 2002 Author Report Share Posted June 12, 2002 thanks Warren I'm using the Hagen KH/GH test kit, which is supposed to be accurate to 10ppm (~0.5dH) and my Wardley pH test kit is supposed to be accurate to 0.2 pH units. I've been using these the charts for a couple of days and they seem to be giving sensible approximations. I'm only after a ball park figure, so I think it should work ok. A couple of days ago I came across that stuff on the Krib and from the chart my CO2 level in my 160L tank must have been almost non existant. After a day of DIY CO2 supplementation it seems to be on the way up, so I'll have to keep an eye on things and see how high it will go. Quote Link to comment Share on other sites More sharing options...
Warren Posted June 13, 2002 Report Share Posted June 13, 2002 I used them once too. They were not too bad from memory. I don't use test kits much anymore for CO2. I have a system that seems to work pretty well. I have the Dupla CO2 Dauertest indicator in the planted tank. As long as its colour is green I'm happy. It saves all the mucking round with test kits. About every 2 weeks I do a pH test as a backup measure. If all is going ok (as it usually is) the pH is bang on 6.8 I looked at pH probes but they were either too expensive or too unreliable. Quote Link to comment Share on other sites More sharing options...
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