For those of you shutting off your CO2 at night...

[jarmenta]

Are you running bubblers or powerheads during the night? I've read that some have awaken in the morning to find their fish gasping at the top of the tank from the lack of O2. I want to try and avoid that from the get go but I haven't added any bubblers/powerhead at night. I was curious as to if/when/how I should agitate the water. I get the impression from some articles and other forums that too much agitation at night is bad. So I want to know what some of you are doing.

To give you a little background I set up my 100 gallon planted 3 weeks ago and I just added an Elephant Nose fish (only fish). I understand the plants use O2 at night and my tank is fully planted (60 plants and 1 square foot of micro sword). My lights and CO2 come on at 8 am and go off at 6 pm (reduced hours as I'm almost done knocking out an algae problem). I've monitored my PH throughout the day and some nights and it goes from a low of 6.7 in the afternoon to 7.0 at night/early morning. Some parameters as of yesterday afternoon, around 1 pm:

Temp: 78
PH: 6.7
CO2: 22 PPM
O2: 9-10 PPM
GH: 100 mg/l or 5.59 deg
KH: 60 mg/l or 3.35 deg
Ammonia: .1 mg/l
Nitrite: .1 mg/l
Nitrate: 5 mg/l

Those number have been pretty steady for the last two weeks. I'll try to watch the fish closely tonight and take an O2 measurement just before bed to get an idea. Any comments or suggestions are welcome.

Jesse

[Mgamer20o0]

ok i could be wrong but if you keep the co2 on then you might need a air pump. when the lights are on the plants make o2. if you keep the co2 on it might get to high of co2 thats why people add air pumps. i have mine go on a hour before and a hour after the lights turn off and on. that way at night the co2 levels dont get high.

[plah831]

most people have timers that they set to turn the CO2 on during the day and off at night. another timer may also be used to turn air pump on at night, and off during the day. these are just the same timers that are used for lights.

plants respire in the dark, when there is not enough light to photosynthesize. that means at night, they are competing with your fish for air. if you have enough surface agitation, then you probably don't have to worry about the air pump. surface agitation is not a problem at night, because you're not adding CO2, so don't have to worry about it dissipating due to the agitation. the only time surface agitation is undesirable is when you're injecting CO2 gas and it would be a waste of your money to just let it escape your tank through bubbling or agitation. because it's difficult to change the amount of surface agitation at day/night (changing water level, filtration, etc.), most people remedy this by adding an airstone during non-lighted hours.

your oxygen levels are great during the day! 9-10 ppm is actually super-saturated at most temperatures, so it seems your plants are doing a good job at producing O2. another reading at night is a good idea. as long as it's above 6 ppm, I think it should be just fine for your lone elephantnose.

[djlen]

I have gone both ways with this CO2 issue and, in fact, am doing so currently.
I have 2 - 55 gals. running off of one regulator which I turn off at night. And a 40 gal. that I also shut off at night.
By the same token, I also have a 10 and a 5.5 gal. that I let the CO2 run in 24/7. I do this because I find that the pH swing is too great for me to be comfortable with if I turn the little tanks off at night. The fish don't seem to mind either way, but my 'large' tanks rise from 6.4°pH to 6.9°pH when I shut them down, which I'm comfortable with. The little ones rise from 6.4°pH to close to 7.4°pH and then back down to 6.4° during the day. I'm not comfortable with that swing so I let them run and only have a drop in them of about .2°pH due to the CO2 running at night.
So, IMO it's not the pH that is the potential problem....fish are adaptable, but it's the swing that I don't like.
I would check your pH at lights on and at lights off for a few days and make your own determination on how to proceed. One benefit of pressurized CO2 is that it is very, very consistent. When I was going DIY the inconsistency just about drove me nuts.:)

Len

[jarmenta]

Thanks for the input. I did some tests at night and early morning. At about 12:30 AM my PH was 6.9 and my O2 was 8-9 PPM. A around 6:30 AM the O2 was 7-8 PPM and the PH was 7.0. This of course is with no bubblers or powerheads. I feel comfortable with those numbers for now. As I add more fish over the weeks and the bacteria colonies grow I assume the O2 numbers may start to change. If and when I come to that point I'll try what some of you are doing and monitor my parameters accordingly.

As for having high O2 numbers mid-day I thought that was unusually high. I really hope this Red Sea O2 test kit is reliable. However, I do notice that many of my plants are pearling during lighting hours so I think those numbers may be close to actual. As for the elephant nose, he's doing fine and exploring the tank. I think I saw him using his electrical organ. I guess I missed some paper clips when I removed them from anchoring down my Micro Sword. He/she didn't miss them as it started to prod and poke at some of clips. Indeed a very interesting fish. Anyhow, thanks again for the input!

Jesse

[plah831]

As for the elephant nose, he's doing fine and exploring the tank. I think I saw him using his electrical organ. I guess I missed some paper clips when I removed them from anchoring down my Micro Sword. He/she didn't miss them as it started to prod and poke at some of clips. Indeed a very interesting fish.
that's awesome! i love elephantnoses and other electric fishes. i can't wait until i have room/time/money for a 100 gal. they're among the most intelligent of fishes because the electric ability requires them to have a big brain :)

i have the Red Sea O2 test, too, and am often unsure of its accuracy (because whenever we open the test tube or shake it up, it introduces oxygen). but if you're getting different readings, i guess it works! 9-10 ppm is definitely attainable due to photosynthesis (8 ppm is a ball-park 100% saturation). the upper layers of the ocean are also often super-saturated due to microalgae. so again, good work!