fishes die when i use CO2

[toledosun]

What's wrong? Lost my previous load of tetras when I started using CO2 in my planted tank.

This time round, I didn't turn on the CO2 for the initial 2 days when my guppies were introduced. Used airpump instead. All was well. Today, I turned on my CO2 (about one bubble per second) and my fishes started dying again.

My tank is about 3 1/2 ft x 1ft x 2 ft and it has mainly riccia inside. However, the riccia are newly planted. I'm guessing:

1) my fishes have been used to the high O2 level in the water for the past two days with the airpump going and "suffocated" when I turned off my O2 and introduced CO2 instead;

2) the CO2 changed the KH/PH level of the water and that stressed the fishes;

3) all of the above.

Any advice?

[bclee]

Can't tell from the information you have given. Test the KH/pH, it will tell the story.

Always test for these 2 parameters when you inject CO2. It is the only way to tell whether you are over or under dosing.

BC

[vinz]

As BC said, we need more info.

In the absence of that...
1. Fishes should be able to breathe with just ambient levels of O2, unless your tank is very overloaded. CO2 does not replace O2. Both can co-exist in the same water. There's a possibility, if the CO2 level is too high, that the fishes succumb to CO2 poisoning. But that does not indicate O2 levels, high or low, in anyway.

2. Likely the CO2 affected the pH level. Did you raise KH to buffer the pH swing? You need at KH of 1 to buffer the swing. CO2 should not affect the KH level directly (someone correct me, if I'm wrong here).

[toledosun]

can't do any tests because SOS came from wife at home. Working right now. Guess the question I'm trying to ask is- seeing that CO2 injection will definitely affected KH/PH, would the change in KH/PH in itself, be sufficient to kill the fishes, or must it be a case where the CO2 level is too high?

[bclee]

Usually fishes are dies more because of CO2 poisoning rather than pH drop. Tetras can slightly acidic waters.

Check for symptoms. Are the fishes all near the surface of the water? If so, shut of the CO2 immediately and use an air pump. Do a water change if the condition is critical.

BC

[vinz]

Errr... BC, what about rapid pH swing due to zero KH?

[bclee]

With 0KH, 30ppm of CO2 will result in pH of 4.8... hmmm... possible.

I know that some tetras can tahan down to pH of 5.

BC

[vinz]

Acutally, I'm referring to the rapid but large drop from near nuetral (assumption) to such low levels in a short time, no the actual pH it settles at.

[bclee]

I have actually read in an article that pH swing is usually not as bad as what we make up to be.

The article mentioned about the pH swing in the nature for example where rain fall can actually alter the pH quite quickly. Rain water will change the CO2 content, wash minerals from the soil... etc.

Well, I have not experiment... and I don't think I will, so just deducing from the articles I read.

BC

[chia2k]

guys , do ph swing kill fishes the same way as co2 poisoning ? thought fish die of co2 posioning usually seen at the surface gulping for air

[budak]

On the APD, some are posting the observation that pH levels are being used (wrongly) as a proxy for optimum planted tank conditions (re CO2). On my part, I have never bother too much with pH per se, as it is just a measure of acidity. True lower pH corresponds to a higher CO2 concentration at a given KH, but no-one seems to have managed to determine the individual impact of each event (rapidly falling pH vs. high CO2 levels). My tanks' pH somehow hovers around 6-6.5 with no apparent problems.

For toledosun's case, I note that his mostly riccia tank is newly planted. What's the lighting amount? If not enough, the riccia isn't going to be much help in photosynthesising or taking up nitrates/ammonium. The total fish-load? Tank age? Filtration maturity? And why shut off CO2 in those two days?

KH and pH are very different. KH will remain stable, while pH swings due to various factors.

[toledosun]

----------------
On 1/28/2003 9:43:13 PM

For toledosun's case, I note that his mostly riccia tank is newly planted. What's the lighting amount? If not enough, the riccia isn't going to be much help in photosynthesising or taking up nitrates/ammonium. The total fish-load? Tank age? Filtration maturity? And why shut off CO2 in those two days?

KH and pH are very different. KH will remain stable, while pH swings due to various factors.


----------------

Well, lighting isn't that much, about 1W/gallon. However, the tank is in the hall, part of the dividing wall and actually receives about 3 hours of afternoon sun through the windows. As to why I switched off the CO2, guess it's because the last time I had it on and introduced some tetras, they all died within a day.

My guppies were from my dad's place. Noticed that in his house, where he has much higher fish load, but with only airstone and filter, the fishes don't die as easily. That's why I thought I'll play it safe by switching off the CO2 first, let them get used to the water and then turn it on. Wallah, once on, they start dying. A few more died overnight even though I've replaced the water in the tank 3 times already (about 10% each time).

Anyway, I've decided to do an overhaul tonight. Will take out some of those riccia that are planted in the lower light areas and replace them with X'mas moss. Noticed that with the fan on, my water temp is about 27 deg celcius so that should work. This way, don't have to worry about CO2 and this will provide more cover for the guppy fries that are already in the water. Hopefully, this will be enough to offset the mortality rates.

[toledosun]

Just an update. Went to the LFS opposite the Central Sikh Temple (system engineering, I believe) and asked the owners there about the possible causes of the death. They suggested PH problem. I bought one of the bioplast test kit from them ($15 expensive but glad I did) together with sodium bicarbonate (or something like that).

Went home, tested the water and the result was "redder" than 4.5. I believe that means it's lower than 4.5. Anyway, added the sodium bicarbonate and wallah, next test shows about 6.5. After that, fishes stopped dying!

Thought I'll pass this info on in case anybody else faces a similar problem May want to test PH.

[gnome]

You do realize that sodium bicarbonate is the same as "baking soda," right? You can buy it very cheap at the grocery store. Sodium bicarbonate raises your KH (KH is also referred to as "carbonate hardness&quot and works to keep the pH from crashing. CO2 in pure water (KH=0) reacts with water to form carbonic *acid*. If you add the conjugate base (bicarbonate), it helps to "buffer" the solution so that the H+ is effectively being "absorbed" by excess base. You get the same effect with crushed coral (calcium carbonate), but much slower because the solubility of the calcium and carbonate is very low in water. Also, unlike its sodium counterpart, calcium carbonate will raise the GH (measure of calcium and magnesium ions).

I guess it's not important if you're no longer going to use CO2, but for possible future reference, it's critical that you measure KH and pH several times while starting up CO2 injection. Unless you have a CO2 monitor, the cheapest way to determine your CO2 levels is to use the chart that correlates pH and KH with CO2:

http://www.thekrib.com/Plants/CO2/kh-ph-co2-chart.html

When using CO2, your KH should be 4 degrees or higher.

If you have an aquarium, the minimum you should have is pH test kit. It's good that you got one, although that's pretty expensive! Good luck with the guppy fry! I think they'd prefer the moss, anyway.

[gnome]

One more thing: the reason why the guppies succumbed so quickly is probably because they're native to brackish waters. This means they can tolerate fairly high pH (above 8.0) and they like hard water (high GH) as well as other minerals. Your water was not only very soft, but by adding CO2, your pH dropped *way* below what they are used to. Guppies can live in *slightly* acidic conditions, maybe as low as 6.6, but this is not very "suitable" for them. Maybe this explains why they died quickly after starting your CO2.

[toledosun]

Yeah, thanks guys. Learnt from my mistake now. Have to agree the Bioplast PH test kit is ex. The Sera test kit from Petmart is less than $10.00. Bought it nonetheless because:

a) it was CNY eve so in charitable mood;
b) least I could do in return for the advice; and
c) if you'll recall, it was raining like crazy that day and there's no way I'm going to run in the rain more than I need to .

Guess I now realize why my tetras died in the past as well (when I was using CO2). At that time, I checked water before and immediately after and stopped there. My area's PH is very high, more than 8 (probably because pipes are new or something) so I actually bought the powder to lower the PH! PH probably crashed after that without my realizing it.

Learnt my lesson. Will be good and test more regularly.

Say, anybody know how much those PH test pens cost? Think it'll be easier than trying to match colours.

[Allen_1971]

Toledosun,

one thing worth noting, do a quick check on your tap water kh... I'm guessing that its zero, or close to it. If so, then the reason you have so high a PH is likely due to the method of processing which causes dissolved gassed to be removed... If you let your water settle, you should probably find that the PH is lower.

Also, if your PH is below 4.5, means your bacteria are dead. Highly likely that your tank will start to cycle in the weeks to come... If its heavily planted, you may not need to worry too much... all in all though, I would start to monitor for Ammonia and nitrite spikes.

[gnome]

Thank you, to the kind moderator who fixed my post to make the URL link !

Allen's right: while typically, high pH correlates with high GH/KH, this is not always the case. Where I live, the water comes out of my tap with pH of 8.0+ but KH of only 2 degrees. With such low carbonate hardness, CO2 injection would be *very* unstable. So I keep a small plastic cup of crushed coral in a discreet part of my tank. If I maintain a regular partial water change schedule of about 15-20% every week, my KH stays pretty constant at about 4 or 5 degrees. I like to keep my GH at about this level or higher so that my snails' shells develop nicely, and my shrimp molt properly. When I was lazy with partial water changes, I had my GH/KH go up to about 16 degrees. At this level, it becomes very difficult to keep any significant amount of CO2 dissolved in the water.

While I'm usually jealous of Singapore aquarists being able to get exotic and rare fish and plants so easily and for so cheap, I guess the U.S. wins out in cost and accessibility of testing kits. pH tests are generally all of fair quality, and the cheaper ones can be bought for less than $5(US). Trace metal test kits get a little less reliable with lower cost, but they're not as critical to have, in most cases. On a day-to-day basis I don't care to run my fish tanks like a science laboratory . But every now and then, something goes wrong [:0] and you gotta have those test kits!

[toledosun]

Thanks for the advice guys. And you're right, my KH is less than 2 deg. The instability of the conditions was what drove me to turn off the CO2. Too busy with work to spend too much time monitoring water conditions. Trying now to keep things simple and stable to lessen workload.

[Allen_1971]

Gnome,

Actually we get pretty decent test kits in singapore... sufficient for the average aquarist... sure its pretty difficult to get our hands on the much vaunted lamotte kits, but then again its not really that critical to get such accuracy. On the whole, I'm pretty satisfied with whats available on the local market... Perhaps all thats missing is a test kit for Dissolved Organic Compounds... that would be interesting to have. []