i understand that you cannot messure the co2 levels when you have 0 KH, but does this have any effect on co2, i was reading somewhere Tom said that CO2 doesnt disslove very well under 0 KH. i always thought the lower the KH the better it is for plants. i just want to hear your opnions on this, i been keeping fish and plants under these condtions for long time now. i never really seen any fish stressed under these condtions, my plants are ok too, but not the best. i just want to see if anyone is sucessfully keeping plants under 0 KH
I'm not sure I said it does not dissolve very well, I may implied that, but for our purposes, does not seem like an issue, plants seem to do very well at very low KH's and the whole thing with CO2 and HCO3 really gets prickly. We could discuss theory, but at the end of the day, my questions tend to ask at the plant organism, fish, shrimp level.
I have pretty low KH(16-22ppm range over the year), I think alkalinity would be better or split it into carbonate and non carbonate alkalinity. Seems that all plants do exceptionally well in KH's of 3-4 degrees or less. Most, perhaps 90-95% do exceptionally well at KH's 3-4 to per 15. Perhaps the alkalinity regardless of pH when using CO2 interferes with uptake of some nutrients, metals who knows...........but for most plants, it's more a functioning of CO2 uptake.
So when we add CO2, regardless of the higher KH's, the plants have ample CO2. So seem to take this as a pH preference, but it might be best to just think CO2/enrichment since so many hobbyists add the gas.
I've lived in places where my GH and KH have been from 1 degree of KH/Gh maybe 2..............to Santa Barbara/Goleta, where the KH was 11 and the Gh was 25, to Marin County where the KH was 5.5 GH 9, Davis Ca, where the KH was 17 and the GH 19, but the GH had 52ppm of Mg..........foul stuff..........then Florida with a KH of 3 and a KH of 5, to SF where the KH is 1 and the GH is about 2, same as the American River water source I have now. The Sf bay area has a very wide range of GH and KH values, East Bay MUD has KH of 2 and PO4 around 0.5ppm, Marin had a PO4 of about 1.2ppm, SF, none really.
If you live in these places for a few years and keep a variety of plants.......you get a feel for what works, what does not, but this does not begin to explain what is going on with the plants. Maybe the issue was me?
Maybe I could not grow some plants due to some horticulture issue rather than the plant actually preferring a certain KH?
Could be. I cannot ever be 100% certain. However, if I falsify that hypothesis and grow say really nice Rotala macrandra in KH of 12 tap water...........and keep doing it easily for 1 year, my hypothesis is a cooked goose, I have to reject it and accept the alternative that something other than a KH 12 is causing folks more issues in the aquarium.
Then I can be certain that a KH of 12 is NOT the issue, and it is something else. It's the something else that gets folks.
Testing CO2 can be tricky as well.
A good pH meter and flat tip probe are good items to have.
We tired a no# of tricks such as 100% water changes and leaving the CO2 needle value set at the same rate, then added 1 degree of KH with baking soda, then measured the CO2 a day or two later.
The assumption was the pH/KH relationship will hold if we have a reference KH solution without any non carbonate alkalinity or tannins. Yea, some will leach that day or two....but we assume it to be non significant. I did some comparisons with an oxyguard CO2 meter in flask, and it worked pretty good against a reference.
In the behemoth 1600 gallon tank, it also matched to inside about 1ppm of CO2 at 40ppm. Not bad for most.
Still, I would look for ideal nice thick plant health/growth......then go about seeing what ppm it is with good methods. Do not assume that any specific range/ppm (like 30ppm) is suited/optimal or Best for all aquariums.
I'm afraid using the plants as the test, then using test kits/methods/meters to corroborate or to get close...........is the better approach. I and many others have hit our heads against a wall thinking that we have enough cO2, only to realize we did not. Sounds like a broken record, believe me, I know, and I've eaten crow/my own advice in the past to accept. Finding why one tank does well and another does not is not easy, sometimes you get lucky, but if you have fish, this is more troublesome.
Findign the source of the CO2 related issue can be a game of "Who Dunnit". I had a cracked 2" long FPT 1/8" right at the thread from torquing the sucker too hard and I had no issues growing the same plant in another tank with all the same ferts/light/soil/water changes filtration etc. I knew it was CO2 but could not find it. Finally, took the entire regulator and every part from start to end, and yes.....the last thing I found...........was that small crack.
Pissed me off.
Still, I'm not sure why the plants respond to KH different, but if you have low KH, be happy. I've not seen any reason to add baking soda........at least for the plants. It did seem easier to target good CO2 ranges in the past, but this is just opinion. I would not argue for or against it.