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Ph, kh and co2...

1K views 5 replies 4 participants last post by  artemism3 
#1 ·
I have a rather odd question caused by something I can't explain and have no idea as to the cause.

My tank is a 75g with tahitian sand substrate. It is moderately planted and have had Co2 running for about 6 weeks.

My tank's water is 7.5 ph when it has been outgassed with a kh of 10. My tap water after it has aged for 3 days has a ph of 8 and a kh of 10 degrees.

Why is my tank's ph lower then my tap? I have not been able to figure this out. Also considering the above, what should I be lowering my ph to with the co2 to have a healthy enviroment for my fish?

Thank you!

Jeremy
 
#4 ·
I know about the Co2 chart. I have checked that out previously.

I guess my concern is surrounding the fact that my tank has a Ungassed- No Co2 in it - ph of 7.5 and 10 degrees KH. These parameters tell me that I have co2 present in the tank, at about 10ppm with NO CO2.

Should I disregard this?
 
#5 ·
fish give off "some" co2, but shouldn't be influencing it that much.

the 10KH giving 8pH is based on the atmospheric level of co2 being 3ppm, so it is right on target for your tap water results.

Also, what is your fish load like? As you feed fish and they produce waste, the acids will eat away at your KH a little bit. This is one of the main reasons for having a KH of above 4 in a non-planted tank. By saying that your pH is 7.5, that would imply a KH of 4 though, which is very doubtful that other factors are pushing the KH down. And you said it is still 10 KH anyway upon testing.

How sure are you that your KH levels are not dropping?
 
#6 ·
I just tested the tank's Kh...came back as 10. This has been constant for the last 4 months or so...the Kh has never dropped.

Fish load is rather light right now... 2 gold fish ( don't ask...they are just there ) 6 cories, 3 dojo loaches, 6 tetras, 3 bettas, 2 dwarf gouramis...
 
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