Co2, Buffering, Ph & Fish Health

[AndyTaylor]

Here's what i've observed:

After switching to pressurised CO2 I noticed that my fish, and my blue rams in particular, were spending a lot of time at the surface breathing. I assumed that they were acclimatising to the CO2 (although there were 2 nutrafins running @ 18/20 ppm before the switch to pressurised) and that they'd be fine.
I helped them with an airstone for a few days while leaving the CO2 running. I gradually turned the airstone down and then removed it.....fish straight back to the surface again.
2 days later I lost 1 of the female rams and my shrimp were all at the surface trying to get out.
Immediate 50% water change, general tank clean, introduced a load of stem plants and most importantly, it seems. I buffered with bicarb.
Now I have my CO2 up to 35ppm and the fish seem perfectly fine with this increased level. At no point during this whole series of events did I have a PH crash....Ph went from 6.6 to 6.3 at most.

Is this something that should have been obvious? I know that buffering the water helps prevent major PH drops but does it effect the uptake of CO2 to that degree?

Any thoughts?

Andy

 

[gizmo001i]

Isn't 35 ppm a bit over the top. I thought anything over 30ppm was getting to where the CO2 can be dangerous to the fish. I may be wrong, but it seems to be the general consensus in most of the literature I have read in the lst few days.

 

[AndyTaylor]

30ppm is generally believed to be the point at which CO2 becomes harmful to fish (and in theory it probably should) but there are planted gurus on here who run 40ppm with no problems. I think as long as you don't go from 20ppm to 40ppm overnight the fish can handle it. I'm aiming for 40ppm so we'll see.
Having said that, I watch my fish a lot when making changes to make sure they're ok and I have an airstone handy in case of any problems. I'm not sacrificing fish to make plants grow!

 

[AndyTaylor]

Are all the regulars on holiday?

 

[lljdma06]

Are all the regulars on holiday?

Nope, .

I'll add my two cents in about a possible adverse reaction to CO2 injection in anabantoids. When I first planted my 15g and achieved above 30ppm, I had a betta in the tank. It then developed "popeye". At first you think "popeye", bacterial infection, treat with an antibiotic, fine. So I removed the fish and put him in a 3g bowl to treat with medication. Two hours later, his eyes are back to normal! Still treat with medication to be safe. So I'm thinking coincidence and nothing more. A few months later, another betta in a CO2 injected tank comes down with "Popeye". Check the CO2 again, it's above 30ppm, 45ppm, to be exact. Remove the fish, "popeye" is cured within hours, no medications needed. Coincidence? Not so sure this time. Third time, a sparkling gourami gets the "symptoms" of "popeye", resulting in blindness. This time, it was unclear whether or not it was due to a bacterial infection or elevated Co2 levels. He didn't respond to being removed from the environment and he had it in both eyes, so I treated him with medication and he slowly recovered. This time, it was probably bacterial. However, CO2 was very high at that time, and there was a small pH dip. Thankfully, all of the fish survived their ordeal, but this occurence has stumped a few people as to why this has only affected my anabantoids. I did some research on the net, and the term gas supersaturation came up several times as a possible cause of "popeye" like symptoms. So we'll see.

My two cents. All my fish are fine now. Gourami is still kicking and has adapted to his blindness very well. Tough fish.

llj

 

[AndyTaylor]

Thanks llj....there's someone out there anyway!

It's more the possibility that adding bicarb somehow mitigates the effect of CO2 saturation on fish that was interesting me but I can't really test that theory as I only have 1 tank set up at the moment....
I've increased my CO2 again since with no signs that any of my fish are stressed.....
I have 2 dwarf gouramis and they both seem fine so some anabantoids are ok with CO2 anyway...

 

[Themuleous]

Sorry dude been away learning to ID grasses (massive brain overload but thats another story )

For what its worth, my nano is always running at over 30ppm, mostly because is so small and getting exactly 30ppm is almost impossible as the needle valve on the reg is just not sensitive enough.

Speaking purely off the top of my head here with no proof what so ever, I doubt if the bicarb has any tangable effect on the fish, 30ppm is still 30ppm so the actual amount of CO2 in the water is the same. But I could be wrong?

 

[AndyTaylor]

Ok, so are there other factors that could explain why fish that were obviously stressed with 22/25 ppm CO2 are now perfectly happy, if not happier, with CO2 in the high 30's. The only changes were some stem plants and the fact that I buffered?

 

[Themuleous]

Sorry matey cant help further on that one, anyone else got any ideas?

 

[NAL]

Hi

pH and KH (or essentially alkalinity as it actually is) are in dynamic equilibria. If you have water with a given pH and KH then add acid (by injecting CO2 say-it will form carbonic acid, or through release of other organic acids in the aquarium through fish waste or from bog wood) both parameters will move to a new equilibrium. Continued addition of acid to water with a low KH will reduce both KH and pH. Unchecked, continued CO2 injection can through this route cause pH to crash. You'll end up with battery acid for tapwater, or near enough to it, with a pH less than 6 and KH less than 2, possibly totally wiped out. Underthose circumstances the fish will either not cope with the low pH or the high CO2 (or both). This is a pretty complex area of chemistry that is quite tricky to get your head around, yet it is absolutely fundamental to maintaining stable water parameters (especially CO2). Stability is one of the keys to success in planted tanks. Check out Seachem's website for some really good articles covering this. (seachem.com)

If you've buffered the water, what you've done is create stability against which pH will find it harder to decrease. In my experience, and i've seen my own fish die in front of my eyes as a result of this, it isn't low pH per se that will kill fish but rapid fluctuations in it that send them into pH shock. This is what can happen when you run low KH (low alkalinity) and there is nothing to buffer acidity. My suspicion therefore would be that fluctuating pH could have caused the discomfort you observed.

Nick

 

[AndyTaylor]

Thanks Harlquin,

I'm aware through observation that the rapid change in PH is what causes the problem generally but in this case PH only dropped by 0.1 over the space of a week and the CO2 level didn't seem to be increasing.
Does buffering increase the tendancy of the water to take up CO2 as well as creating stability against a PH crash?
It seems that the CO2 level only started to increase after buffering. Bear in mind that I was pumping in CO2 at 80/90 bubbles a minute with no real increase in CO2 level until i buffered....

Thanks Andy

 

[zig]

Not sure Andy whats going on, although you did one other very important thing which you haven't really focused on.........you did a 50% water change, and i would imagine this was more important than anything else you did including the addition of the bicarb, perhaps the water pre the water change had very depleted dissolved oxygen levels and any addition of CO2 would stress the fish no matter what, i would keep an eye on the fish as the week goes on making sure there is sufficient surface agitation to create oxygen exchange at the surface of the water, if need be, you may have to run an airstone at night to drive off the CO2, i have been running my CO2 at 40ppm + for ages now with no ill effects on the fish.

Double check your CO2 levels as well

Take a sample of your tankwater and let it sit for 24 hours and then do a Ph test, if the Ph of the water in your tank is 0.8 to 1.0 full Ph unit below what the sample has tested then you are hitting 30ppm CO2.