CO2 and very hard water

[Alien Anna]

Hi Everyone - I followed the links in the pinned article on CO2 and was very alarmed to discover that according to the tables, my CO2 level is off the scale. This is very odd because I've only just added CO2 and if I look at the chart for before I added it, I also get an off-the-scale CO2 reading. In fact, I get an off-the-scale CO2 reading for the water out of my tap (due to the high KH and pH readings).

Does this mean you shouldn't use CO2 if you've got hard, alkaline water?

I have a GH = 21, KH 14-21 and pH 7. My CO2 pump has been on about a week and all my fish seem fine, except Brillo the bristlenose has gone AWOL again (I don't know where that fish finds to hide). My temperature is about 80F (can't get it any cooler, except at night) and I have a Juwel internal column filter system.

I would hate to kill any of my fish in an attempt to get fast plant growth. Can anyone reassure me?

 

[Alien Anna]

Hello? Anyone? I'm worried my fish will suffocate

 

[Ob1]

Hi Alien Anna

I was reading fish mag today and I’m sure it said there are test kit available that can measure oxygen in the water, I recall the article quoting 8mg/l or g/l or something per litre was acceptable for fish.

 

[Lateral Line]

I've never used a CO2 injector, and RO ensures that for 15+ years, I'd never had really hard water - no experience, sorry.

>>> all my fish seem fine,

Good sign. If that situation continues, probably okay. What I'll do is dig out some of my old university notes and try to work out the chemistry, (may still be in England - don't know).

>>> I get an off-the-scale CO2 reading for the water out of my tap

How are you testing your CO2 concentration?

 

[Alien Anna]

>>> I get an off-the-scale CO2 reading for the water out of my tap

How are you testing your CO2 concentration?

Using a table I found on The Krib website (am I the only one to find that site utterly incomprehensible? ). The table asked for your pH and your KH and calculated it from there. Couldn't quite see how that would work. Maybe it gave you a theoretical value for maximum CO2 concentration.

Anyway, using that table it gave a CO2 reading >45 ppm. Apparently fish can't cope with more than 20-30 ppm CO2, but someone should tell my fish that!

I still would like to know what is a safe CO2 level for my fish and I'm not convinced by that chart, the more I think about it. However, I've just bought a CO2 monitor/alarm off Ebay. It's probably a total waste of money (like the carbon monoxide monitor I bought for my brand new boiler in the kitchen) but its peace of mind. I'm considering ordering an O2 test kit but a very experience LFS guy told me that was an utter waste of money and couldn't I just look at my fish to see if they could breathe, instead?

I've been reading horror stories about CO2 dumping in the tank and killing the fish. I'm glad I'm not using a gas cylinder - they sound like accidents waiting to happen. My yeast CO2 generator isn't technically large enough for my tank and the worst that could happen is I get a tank full of yeast and sugar (that happened before but nothing terrible happened - I just had to do a lot of water changes that week). I'm testing the pH twice a day at present, just to see what happens. It's slowly creeping downward, which is good (my tetras like acid water).

 

[aquamanis]

Hi Anna, I just did a bit more reading at the krib (I agree you need a PHD in chemistry to understand half the posts). It seems most KH kits measure total alkalinity of the water and not just the carbonate hardness so any buffers or peat will show up in the total reading giving a false reading. I would say that is what is happening with your readings. There was a suggestion that you should take away general harness from the KH (carbonate hardness) to get a true reading of KH?. If this is the case from what you said I worked out roughly you have about 20ppm CO2, I,m probably wrong but I,de be curious to know what your test says.

 

[mrV]

I do not see reason why you need to add CO2 into your tank. Your KH is quite high and plants can use hydrogencarbonates as source of carbon too.

 

[Alien Anna]

Thanks Aquamanis! I'll check back with you when I get my test results.