CO2 Overdose???

[pdoutaz]

Checked my 120G this AM - have 2 fatalities and another dozen or so fish hanging aroud the surface - seem to be trying to get air. The other fish also seem to be gilling quickly - is this too much CO2??

Just replaced an XP4 and 2 AC110's with a new FX5 - transferred some media from old to new when I swappped out - could this be an issue?

Currently doing a 50% water change and have shut CO2 off completely

ALL comments / feedback greatly appreciated

[neven]

Most likely its a lack of oxygen. How are the temps there? i know yesterday got pretty warm in the afternoon and caught my place off guard (no AC on), so it could be that. another thing is how is the surface agitation, Since you a co2 tank, its more worth it to have a little bit of co2 degassing for the agitation.

Also do you have a drop checker? if not get one. They are handy little things that give a great visual indicator on co2 levels, keep in mind theres an hour to two hour delay when fine tuning it.

One last thing, i always keep an air pump on hand, so if i notice the fish are looking starved from oxygen, i throw the air stones in under the filter outtake, and plug it in. Normally in no time i got happy fish again.

[pdoutaz]

I agree it's probably lack of O2, but I'm confused, I thought a bubbler was a no-no whern running CO2 (surface agaitation)??

[davej]

There's a good chance you had an overdose of CO2 from the sounds of it. If you have a solenoid on your CO2 system it is a good idea to have a timer on it to shut it when the lights go out. As there is no photosynthesis going on there is no need for the extra CO2. In fact the plants to a small degree use a little O2 and give off small amounts of CO2 in the dark.

[neven]

I wasn't saying run it all the time, i just said its a great emergency measure when the fish are suffering, as it'll drive oxygen into the water column at the expense of your co2. As for the agitation, gettin the surface to the point where its moving fast but the surface isn't breaking is where you want to be

[pdoutaz]

Thanks Neven and davej,
CO2 is on a timer, goes on/off same time as lights. 2 more questions for anyone - I have a drop checker, but it ALWAYS shows a higher PH then when I use my (new) PH test kit - why is that?
Secondly, do I need to have a bubbler running now that I've removed the AC110's, I was told with CO2 I do not want any surface agitation, but as the fish all look MUCH better after completing a 50% water change, I'm not sure if problem was lack of oxygen or CO2 overdose (maybe both)?

[CRS Fan]

I would say it could well be a mini cycle. I suspect that the change in filtration did it causing a spike in ammonia. I have had this happen with my high tech tanks when I overwash sponges, convert filtration types (using cycled media), and adding additional substrate. I usually see my fish gasping.

It could also be a CO2 overdose or a lack of oxygen. Do you have a drop checker? Many planted tank enthusiasts will run an airstone overnight when the CO2 is shut off because in highly planted tanks, the plants compete with the fish for O2 at night.

You could also angle the FX5 spraybar up at a 45 degree angle to the surface so a rolling boil effect is noticed at the surface. I do this with my Fluval 205 and I have stopped using an airstone at night. I use an atomizer as a diffuser an it is extremely effective at disolving CO2 in the water column.

Hopefully this helps.

Best Regards,

Stuart

[pdoutaz]

Neven, you posted while I was typing the previous - the FX5 does seem to get the water moving quickly, so if I'm reading your replies correctly - I had my CO2 too high???

[2wheelsx2]

If the drop checker shows yellow while your CO2 cycle is on, then you have it too high. One thing that's missing from this thread is, what is your fish load compared to your plant load? Ideally, you want to show your CO2 off before your lights go off too, and start it a bit before your lights come on. That would help keep you CO2 at 30 ppm during the photo period and dissipate it after the period.

Perhaps a picture of your tank as it is now would help. One thing I do with my filter outlets is to point the outlets parallel the surface or even angled up slightly to help the surface turnover without breaking it. This would promote gas exchange without excessive CO2 offgassing. And I also agree with Stuart that it may be a mini-cycle. Have you measured your ammonia and nitrites? Ideally, you would have put ALL of your biomedia from the other filters into your FX5, but since your tank is planted, it shouldn't have been a problem, but it depends a bit on how densely planted it is, and what kind of plants are in there.

[pdoutaz]

Heavy fish load, but also heavily planted
Current parameters after water change:
GH: 120
KH: 40
PH: 6.4-6.6
Nitrate: 50+ (VERY hard to tell with this test kit)