Lack of oxygen in planted tank overnight?

[misnoma]

I have a wee issue with my heavily planted tank (4x2x2 for Alan ). I'm running two of the nutrafin CO2 things on it, which of course run 24/7 as opposed to just during the day. I've found that however in the mornings a lot of the fish are sitting at the waterline, and don't really move from there till the lights go on.

My take on this is that during the day (lights on) there's enough photosynthesis going on to keep the fish happy, however when the plants stop at night there's just CO2 getting pumped into the water that's not being taken up by anything or converted into O2.. bad.

So... would I be smart to put an airstone in the tank, on a timer so it runs only when the lights are out (with maybe a little overlap), then stops during the day so I can maximise the CO2 uptake of the water?

[Faran]

Hiya misnoma,

Plants take CO2 and turn it into O2 during the day and do the opposite at night.... O2 into CO2. So yeah, there will be a big change in oxygen levels in the water between day and night. My advice, don't run the CO2 generators at night. There's a reason why yer only supposed to run them during the day.... if you can't control the day/night thing then yeah, airstones will help.

[Ira]

Or if you're using some a yeast CO2 system which can't be just turned off at night, put an airpump on a timer to come on when the lights go out.

[misnoma]

Righty.. airstone it is.. yeah.. being the nutrafin CO2 jobbies they're a bit hard to stop at night without making up some funky system.

[spooky]

Another trick you can play with a coke-bottle of yeast is to leave it on the lights. When the lights are on it is warmer and pumps out more CO2 when the plants can photsynthesise it.

Thats the theory anyway, I'm not actually sure how much of a difference it really makes since the Dunedin water is hard enough to buffer away any pH swing and I haven't tried to do any night/day hardness comparisons.

Wouldn't work for the nutrafin stuff anyway.

[Bluetom]

wouldn't a little tap in your tubing do the trick?? switch it off during the night, somewhere like mitre 10 or placemakers would have them i would think.

[misnoma]

Possibly if you vented it to the atmosphere... turning it straight off could have explosive effects

One other question.. I have no airstones at home, so am just running airpump->hose->tank, and its rather noisy... I take it an airstone will quieten it up? (it's a brand new airpump)

[spooky]

Yeah, the airstone will fix the noise since the bubbles are smaller and there will be less air flow overall.

You could try blocking off the end of the hose and putting pin-holes along it. I;ve never tried that, but it should work.

[Snowman]

Misnoma, if your out south let me know i've got spare air stones. : -)>

[Bluetom]

if your talking 6-8 hours night time then i don't think the build up would be to bad. Airstone sounds safeist though.

[petplanet]

CO2 levels in the water have no impact on oxygen levels in the water.

[Bluetom]

water can only dissolve x amount of gas no matter what sort, if you fill it up by continuously pumping in CO2 all the O2 is pushed out, CO2 is more dense, not that it makes a difference.

So yes CO2 does effect O2, it will displace it.

[Tanksman]

water can only dissolve x amount of gas no matter what sort, if you fill it up by continuously pumping in CO2 all the O2 is pushed out, CO2 is more dense, not that it makes a difference.

So yes CO2 does effect O2, it will displace it.

That is not correct sorry - both gases are soluble in water independently of each other - And water will absorb far more carbondioxide than a fish can stand - Water can have plenty of oxygen and far too much carbondioxide and can cause fish to die.

[Tanksman]

wouldn't a little tap in your tubing do the trick?? switch it off during the night, somewhere like mitre 10 or placemakers would have them i would think.

And that sounds like a good way to wake up to a bomb. Bluetom I suggest you do some research :-?

[Bluetom]

apologes tanksman. :-? :-?

Maube i shouldhave stayed awake in chem.

[HummingBird]

Yeah co2 acts as a narcotic on fish. In regard to the exploding thing though, I think the nutrafin cannisters have a guard against that, I remember reading something to that affect in the manual of mine.

[Tanksman]

How many fish do you have in the tank - If theres quite a few then using the airstone at night rather than turning off the co2 would be the best idea. As the plants and fish increase the CO2 level overnight it would add to the already high concentration of co2 at lights out and will cause discomfort at best. Ira's idea of using an airstone with the pump on a timer would be the go. It should come on at lights out and go off maybe an hour before lights on allowing a bit of CO2 to build up - And don't trust those check valves IMHO - try and have the pump above the water line to avoid water backsyphoning and wrecking your pump :roll:

[misnoma]

Yeah, everything's above the waterline

I shall try and procure an airstone tomorrow, shut the pump up a bit I got another timer today, so it's set for when the lights are off.

Snowman.. might visit you tomorrow night if I can't get past a LFS during the day - cheers

[Shilo]

Misnoma, don't worry about it. As Tankman said CO2 and O are independant thus the CO2 won't displace the O. Also although plants use O at night, the tank water should be so saturated with O during the day that what they remove during the night is to small to worry about. When plants pearl its the excess O that can't be dissolved in the supersatuated water.

The main problem with excess CO2 in the night is PH swing. If your water has a high enough KH then it shouldn't be a major. Would be surprised if the Yeast system produces enough CO2 to be dangerous to the fish unless a large DIY bottle is used in a very small tank.

[misnoma]

hmm.. time to start testing pH night/morning too then..

However.. I ran the airpump last night from lights out, and when I got up this morning I didn't have the same "fish all at top of tank syndrome" so I think it definitely helped. (believe me, with ~200 baby bristlenose it's pretty obvious )