Co2 - Its Effect On Ph

[tanksalot]

I've been merrily experimenting with DIY CO2 in my 27L shrimp nano and everything looks fine, but I'm wondering whether the pH drop I discovered when I tested yesterday is normal.

My water comes out the tap round about 8.0 with a KH of 13 degrees (so it's well buffered); when I tested the tank yesterday (I hadn't thought to do it since setting up the CO2) the KH was the same but the pH had gone down to 7.2. I know that dissolved CO2 becomes carbonic acid, but I wasn't expecting a shift quite that big!

So is this normal, or is something amiss?

 

[smithrc]

Yes . It's normal.

The level of co2 in the tank is directly related to the KH and ph...

Try leaving a glass of tap water on the side over night and check the PH in the morning once it's settled.

 

[RadaR]

As mentioned, yes CO2 injection will decrease pH due to the production of carbonic acid. However carbonic acid is a weak acid therefore pH drops related to CO2 injection should not be feared or worried about.
You will usually observe a pH drop of about 1 when CO2 hits 30ppm. This can happen in just a couple hours, but like I said, it's nothing to worry about.

There's no fantastic way of measuring CO2 (for us hobbyists). We used to use the KH and pH charts however these are innaccurate because other things are present in the water that will change the pH, not just carbonic acid. Phosphate for one example.
Drop checkers are handy. Check this out.
Plants, algae and fish (dont want them gasping) are your best indicators/test kits.
Another link.

 

[tanksalot]

Okay, thanks guys

Those are very helpful articles, RadaR. I'd actually read the first one, but I don't think I took it all in at the time - things like that start to make a lot more sense to me when I get going with some practical experience!

Reading it again, I think I probably do need to back off the CO2 a bit. I have a drop checker with homemade 4dKH water in it, but I think I may have been misinterpreting the colour a bit. Looking at the illustration, mine is definitely towards the yellow. I'm running two fermentation bottles (to smooth the transition), so I'll ease back on the yeast a bit over the next couple of changes and see where that leaves me.

This is such a small tank that I will probably go back to using Excel in due course - far more practical - but I wanted to give CO2 a go and see if I could get it right. I may come on here and panic once in a while , so thanks for the help

 

[RadaR]

I'm running two fermentation bottles (to smooth the transition), so I'll ease back on the yeast a bit over the next couple of changes and see where that leaves me.

Fair enough but if you aren't experiencing any problems with fish gasping then I wouldn't lower it (personally).

 

[tanksalot]

I'm running two fermentation bottles (to smooth the transition), so I'll ease back on the yeast a bit over the next couple of changes and see where that leaves me.

Fair enough but if you aren't experiencing any problems with fish gasping then I wouldn't lower it (personally).

There aren't any fish...do shrimp gasp?

Seriously, what signs would they give that they're in distress? (short of snuffing it, obviously! )

 

[RadaR]

My bad!
I've not experienced it myself but staying near the top of the aquarium can be a sign. Running round the tank at 100mph can be sign of distress too. You have to observe carefully though. My shrimp enjoy cool temp water changes and will respond postively by swimming about.

 

[tanksalot]

Okay - I'll keep my beady eye on them as much as possible.

I've been keeping them for over a year now in various tanks, so I guess I ought to be familiar with their normal behaviour by now. Thinking about it, I suspect it's the males that will tell me more than the females as I find the males tend to be quite a bit more active, swimming all over the tank, whereas the females tend to spend more time in one place grazing. If the males go quiet, then that probably won't be good!