CO2 Death by PH drop

[jcarlilesiu]

Ok... I know that we recently had this discussion in a different forum, but I wanted to take a moment of everybodies time to open up a dialog on the subject as it seems there is still some differing opinions.

I have a heavily planted tank with a pressurized CO2 system on a reactor. Due to the design of the reactor, I think I get about 80% or higher disolve of CO2 into the water column. I have been pretty good at monitoring the CO2 levels by comparing the KH to the PH.

My tank has a good buffering capability. In the latest tests, I am showing about a 6 or 7 dKH result. With my PH dropping to about 6.6 during the day, my CO2 is at the upper end of "acceptable levels".

Even with the high levels of CO2 in the tank, my livestock seemed to be fine. I assume thats because the PH reading is somewhat of a false indication of the actual PH due to the injection of CO2.

Recently I noted that the selenoid on my regulator was failing to turn off the pressurized CO2 during the non-photo period at night. Several times, I manually turned off the system to prevent wasted CO2. About this time, we had a discussion on the forum regarding continuing to inject CO2 during the night and how the continued decrease in PH due to injection with little or no plant uptake wouldn't affect the livestock.

The last couple of days, I have been so busy I forgot to manually shut off the CO2. I assume that the CO2 concentrations during the night hours was extremely high. Last night, I lost my mono seabae. He is still a juvinile and as of Sunday when I made another post with pictures, he was doing excellent. I noticed yesterday that he was laying on the bottom of the tank, with labored breathing, a sunk dorsal fin, and opaque eyes. He was twitching and able to move around, but it was more in a paniced fashion. It looked almost like he was unable to see as he kept running into things and swimming erratically around the tank. This morning, he was dead.

I went ahead and ordered a new milwaukee regulator to replace my broken one. I ALSO ordered a PH controller. I want to ensure that their is some system in place to shut off the CO2 should the levels of CO2 exceed what I consider the safe level of PH in the water column (not to mention this should save CO2).

So, after all of that, my question is.... did my CO2 kill my Mono? I have been told before that this is impossible, and I suppose I am just not convinced. All other fish in the tank are acting normally, and show no indication of problems. Then again, they don't have the high PH requirements of the Mono.

 

[jsoong]

I won't say it is impossible .... anything carried to extremes are harmful.

Generally, pH swings from injecting CO2 is well tolerated. <The swing is real .... CO2 doesn't give you a "false" PH.> The fish's tolerance is in part due to physiology .... You can regulate pH due to altering CO2 metabolism & respiration far easier than a "metabolic" source of pH drop. So fish prob treat the pH change from injected CO2 same as that generated from exercise & deal with it easily. (Extrapolating here ... I am a mammalian physiologist ....)

However, most hobbyist reported no problem only with fairly modest swings ... you are changing maybe 0.5 or so with the usual CO2 injection. I suspect that you might well get into problem if you massively dose CO2 & get a rapid large pH drop, esp. with sensitive fish. You cannot really prove anything at this point unless you record actual pH & CO2 levels overnight with the faulty regulator & actually see how much CO2 had been injected. But I would think that it is possible that the CO2 is the killer.

 

[fort384]

Based on the symptoms you described, I wouldn't point to CO2 as the culprit.

If pH swings aren't the problem, then what problem with high levels of dissolved CO2 present? Would it lower the amount of dissolved O2 in the water column? Probably not. But I think at a point, if CO2 concentration in the water is very high, you could cogently reduce the effectiveness of the fish's gills to exchange O2 & CO2. I think if this point were reached, you would see symptoms in multiple fish, and they would be "gasping" at the surface to exchange O2.

With a KH of 6, and a pH of 6.6, you are only achieving 45-70 or so ppm CO2. I think that is still well within the range that is safe for fish. Based on a lot of what I have read, I think you would need to be in the 100+ range to start getting dangerous. I keep my tank in a very similiar range to you, and have not seen any adverse effects on livestock (short term anyway, about 8 weeks). There appears to be some pretty positive outcomes from keeping CO2 at 30+... since setting that as my aimpoint, BBA has all but disappeared in my tank, and everything appears healthy.

Again though, my experience has been in the short term -- some others may have a better grasp of long term effect.

 

[jcarlilesiu]

I think it was the PH drop that caused the issue. Due to the continued injection of CO2 during non-photo period times, I think that CO2 concentrations caused the PH to decrease to a level which that particular fish couldnt cope with.

I have been told in the past that this isn't possible... maybe I miss understood. Ill see if I can find the conversation.

 

[jcarlilesiu]

jcarlilesiu



Joined: 05 Jan 2009
Posts: 6

Posted: Tue Jan 13, 2009 3:40 pm Post subject:

I have a problem. When the fixture initially shipped, I was having a hard time getting the ballast to fire the metal halide bulbs. The ballast has an internal "protect" mode which I assume to be a good thing for fire safety and the like. From my understanding, it also won't allow the bulbs to be reheated in the case of a power failure until the bulbs have had enough time to cool down preventing damage to the bulbs.

All of this is great, with one exception. The ballast is very sensative to this protect mode. Usually, the ballast once plugged in will attempt to heat the bulbs like normal... but usually, it fails, the bulbs go out and the ballast enters protect mode. If I cycle the power on and off quickly on the ballast, usually the bulbs will fire and continue burning within a couple of tries. Once they start heating, they are fine until I turn them off.

I have been in contact with catalina aquarium on several occasions. Thus far they have been very helpful. They sent out a new ballast assuming that the original one was bad. I was excited when it arrived, but low and behold, same issue. Plug it in and the lights flicker once and then go out while the ballast enters protect mode.

I called them back today to explain the continued problem. Since these lights are on a timer in conjunction with my pressurized CO2, I am concerned that if the lights don't fire and stay lit, that my CO2 levels will get too high in the aquarium effecting my livestock. Catalina is going to send out new bulbs to me to try to resolve the issue, thinking that its possible that the bulbs are the problem sending the ballast into protect mode.

Like I said, they have been very good to work with, but I am becoming concerned that this fixture isn't going to work the way I intended (on a timer) and I will have to physically get the lights on each day.

Anybody with experience in electrical engineering or ballasts input is greatly appreciated.

Curtis



Joined: 09 Dec 2003
Posts: 2671

http://www.plantgeek.net/forum/viewtopic.php?p=78815#78815Posted: Tue Jan 13, 2009 8:46 pm Post subject:

I do not have expert advice on the MH, but this statement "that my CO2 levels will get too high in the aquarium effecting my livestock" is not likely to be true. The plants use far less CO2 than what we produce for them.

I run my CO2 24/7 with only a slight pH shift - 4 WPG 75 gallon aquarium.
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jcarlilesiu



Joined: 05 Jan 2009
Posts: 6

http://www.plantgeek.net/forum/viewtopic.php?p=78852#78852Posted: Thu Jan 15, 2009 3:42 pm Post subject:
Hmm.. I was under the understanding that CO2 injection while plants are not uptaking the nutrient could lead to problems with live stock. From my understanding, not necessarily from a PH drop, but rather with an over concentration of CO2 which leads to a lack of O2 in the water column.

Why would we need PH controllers if it isn't a big deal to leave them on 24/7?

Im not doubting you, just completely different from what I have always been told. Just trying to open up dialog.

I do want some help on the ballast issue though if anybody else has any input.Back to top

Curtis



Joined: 09 Dec 2003
Posts: 2671

http://www.plantgeek.net/forum/viewtopic.php?p=78865#78865Posted: Thu Jan 15, 2009 9:16 pm Post subject:
Some people really like tech and need all the gadgets - I prefer to give you straight up advice and save you some cash.

The truth is that the pH falls when CO2 concentrations rise - If you monitor the pH rise and fall after leaving the CO2 running all day and night, the difference really is not that great. Fish are not effected too much by pH shift due to CO2 rise and fall.

There is a device called a "Drop Checker" that can be placed inside your aquarium to monitor the pH shift - this lets you know in a color indicator how much CO2 is in the aquarium.

A lot of scary stuff is written on the internet about CO2 mishaps, but I bet for everybody that has had a mishap, their are 100 that have never seen a problem. If you follow basic guidelines you will be fine.
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Cliff Mayes



Joined: 11 Feb 2007
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http://www.plantgeek.net/forum/viewtopic.php?p=78869#78869Posted: Thu Jan 15, 2009 9:57 pm Post subject:
The amount of CO2 and O2 are relatively unconnected. Anytime the amount of gas is altered the CO2 up or the O2 down it can be bad for the living creatures. The amount of gas in water is usually much less in water that it is in the air. Both humans and fish are adapted to utilize gas exchange to survive and basically to power energy production in cells. It is extremely complex but you do not need to know all this to keep a tank.

pH controllers are essentially a control device to keep the pH within set limits but there are other ways.

The info that you have been given is good and is adequate for your needs.

Can't help you about the ballasts. I bought some and never used them. I am waiting for LEDs to come in to their own. In the meantime the CFLs or T5s are the way to go but MH lights do have some advantages.Back to top

Curtis



Joined: 09 Dec 2003
Posts: 2671

http://www.plantgeek.net/forum/viewtopic.php?p=78914#78914Posted: Sun Jan 18, 2009 8:16 pm Post subject:
Oxygen is actually more limited by , some medications, temperature and dissolved organics inside the water, more than any other factor. When these items get higher, the O2 levels drop considerably, no matter how many air bubbles you produce.

Most modern filters produce enough agitation at the water's surface to provide plenty of Oxygen unless the above three items get too high. Some exceptions might be Internal filters, reverse flow under gravel filters, and canister filters where you place the spray bar too low under the water surface ( all of which can provide very little or no surface agitation)
A tiny amount of splashing / bubble creation by water movement is desirable.

PlantGeek :: View topic - Im new, I got questions

 

[Purrbox]

From what I understand (layman's explaination to follow), the pH changes as a result of the CO2 injections will not harm fish. It is however quite possible for CO2 levels to get to high and harm fish. It's not that the CO2 gets so high that it displaces the O2, but rather that it prevents the fish from being able to breath in the O2 because the CO2 gets in to the gills easier and blocks the O2. Generally you have to be looking at levels above 100ppm CO2 for this to happen.

 

[fort384]

I think it was the PH drop that caused the issue. Due to the continued injection of CO2 during non-photo period times, I think that CO2 concentrations caused the PH to decrease to a level which that particular fish couldnt cope with.

I have been told in the past that this isn't possible... maybe I miss understood. Ill see if I can find the conversation.

Did you happen to measure pH in the AM, right before the lights came back in? This is theoretically when it should be lowest. Just curious as to how low it got.

Honestly, I think maybe we put too much stock in how much the CO2 concentrations change during night and day. Most CO2 leaves the aquarium through the top, by exchanging with the air at the surface. Our plants are using very little (by percentage) of what we inject into the tank. It was something I worried about when I first started, but since getting my pH controller in gear, I have noticed that the CO2 still kicks on sometimes at 2 or 3 in the morning, and sometimes it is running when I get up in the morning (before the lights come on). This to me means that plant respiration isn't having that large of an impact on CO2 levels... rather, the amount I keep in the water is more closely dictated by how much surface agitation I have in my tank, regardless of whether the lights are on or off. This isn't to say the photoperiod has zero effect, just less of an effect then we tend to think it does.

 

[jcarlilesiu]

Good points.

Well, if that is the case, I have no idea what killed that fish. Did a 50% PWC tonight just to be on the safe side, but like yesterday all of my fish look great.

THe mono went from looking and acting great on Sunday - Monday to dead by Tuesday. Thats odd. Something had to have happened.

 

[Purrbox]

Unfortunately unless you can have the fish examined after death, it can be nearly impossible to identify the cause of death. Sometimes when a fish is examined, the cause of death can be totally different than what was guessed.