im all confused now

[RoLeX]

ive jsut started diy co2 on my 20 gallon.
my original parameters were
ph: 7.6
kh: 2.2

After injecting for 3 days (with plants in there too) my parameters are
ph: 6.6-6.8
kh: 8
Which gives me a co2 of about 40ppm

I was told my ph would crash because of my low kh but it has gone up and kept it steady. I do not have any buffer in my tank. Only some drift wood.
Can anyone shed some light on how kh can jump so fast in just 2 days from co2?

Thanks

 

[travis simonson]

What type of substrate do you have? Do you have any rocks in your tank that might contain calcium? CO2 injection will create carbolic/carbonic(?) acid in your water which can dissolve calcareous substances already in the tank causing a rise in KH. That's one possiblity anyway.

 

[azn_fishy55]

you might wanna be lighter on your CO2, I believe that 40 ppm is dangerous for fish. But then what travis said might have caused a discrepancy in your info, messing up the reading of how much CO2 there is.

 

[BrianNY]

The first thing I would do is check your tap water as a control. KH is a measure of carbonate hardness. If your reading is accurate, and your tap water is as soft as appears, something has shifted in your tank.

I've never worked with a DIY system so I'm unfamiliar with things that can go wrong. Simple logic tells me that you may not be diffusing the CO2 properly. If whatever you're using as a carbon source isn't entering your tank as a gas, it might be driving up your KH. Just a thought.

 

[RoLeX]

Hey guys,

Thanks for your responses. I am quite educated on water paramaters and how different things react, thats why i am stumped. I use a river pebble substrate which wont affect the ph. I have no carbonic rocks, or anything that will alter/buffer my ph levels.
I got home today and tested and my ph was 7.0 and kh 11.2 (31.5ppm co2)

I know 40 ppm is a little high. But i have no fishes as i would like to achieve stable water parameters with diy co2 before added any creatures.

All my new plants are pearling pretty crazy from about 15 minutes after the light turns on.

I was thinking it could have been my drift wood because i slighty bleached it when i was treating it and bleach has a ph of 12. But i ruled that out because the kh started to rise before my driftwood went in. Plus i checked the water paramaters everyday with my drift wood after i bealched it and it was stable.

I guess only more time will tell what the problem is.
Any more ideas/suggestions would be greatly appreciated.

Cheers

 

[workfortheman]

Have you checked to see if there was an increase in KH of the water supply? Or better yet, have these changes in the tank occurred at times that you are doing water changes, or topping off?

I would test the tap water, if only for the reason of testing something other than the tank. The KH test solution may have gone bad or something.

 

[Steve Hampton]

I tend to follow Travis's line of thinking. It's not uncommon when using a substrate that is not Flourite, Eco-Complete, or silica sand to see a rise in KH when injecting CO2. Calcium Carbonate is largely insoluble, but the presences of carbonic acid does increase it's solubility often giving rise to KH in tanks with rocks. You can perform a simple test. Take some of the river pebbles and place in a bowl of tap water and monitor the KH over a few days. Most likely it will remain about the same, proving that conditions in your tank are causing the pebbles to slowly dissolve a bit of calcium carbonate.

Regarding the driftwood...it would have the opposite effect. Driftwood releases tannic, humic, and fulvic acids that would over time lower KH as will acids from nitrification. Your situation is most likely caused by dissolving calcium carbonate.

The only other possibility is the acids from the driftwood are interfering with your KH test kit. Essentially what happens is the acids are being counted in the titration giving a false high KH reading...meaning, the KH hasn't increased. However, in this situation the pH seems to be increasing with the KH so this scenario is unlikely and it's almost certain that calcium carbonate is being dissolved in your tank. It will reach equilibrium soon.

The problem you are going to have is when you add fish and need to do water changes. If your tap water and your tank water have widely differing KH's you are going to have a yo-yo change in KH, pH, and likely GH every time you do a water change...not the most healthy situation for your fish.