Not enough oxygen?

[jiatao]

Hello bros and sis, i'm very new to planted tanks and don't know whether anyone experienced a similar situation.

I noticed that whenever the lights are off, most fishes will be gasping or swimming near the water surface for air, but if the lights and co2 are on, they are happily swimming around in the tank.

Is it because when the lights are off, the plants' intake of oxygen for respiration is not replaced by their photosynthesis and therefore caused the oxygen shortage for the fishes too?

In that case, wat can i do about it? I thinking of adding an air pump to run when the lights are out, is it ok? Thanks alot in advance!

[PeterGwee]

Bacteria and critters are the major oxygen users compared to plants which has their own supply and hardly use much.

As for the gasping issue after lights off, do you have any surface movement/current? If not, add some such that a flake food moves around rapidly. You can always add more CO2 to account for the little CO2 loss from that. (You don't need an airpump at night if you add the surface movement 24/7.).

Regards
Peter Gwee

[jiatao]

oh, thanks bro!

but i got surface movement leh, because i got a fan blowing 24/7, but then at night or when the lights are out, the smaller fishes and the rams especially will hang around at the surface, not sure why leh.

do having floating plants make the water current less effective?

paiseh, very new at this, alot to learn still.. thanks for your patience.

[PeterGwee]

oh, thanks bro!

but i got surface movement leh, because i got a fan blowing 24/7, but then at night or when the lights are out, the smaller fishes and the rams especially will hang around at the surface, not sure why leh.

do having floating plants make the water current less effective?

paiseh, very new at this, alot to learn still.. thanks for your patience.

Depends on the type of fish, some tend to hang around the surface of the water at night fall since in nature, the predators cannot see them well anymore and they feel safer there perharps. As long as you don't see them gasping (rapid gill/mouth movement), they are fine.

Regards
Peter Gwee

[jiatao]

oh, okok! now i think it makes more sense. no wonder only some species tend to hang around the surface at nite.

thanks again bro!

[valice]

Your rams should not be hanging around near the surface at night. Instead, you will actually see them sitting on the substrate and sleeping there...

If you have pencilfish, then yes, it is their nature to sleep under floating plants after lights off...

You might have too little surface movemet still... try tilting the fan at an angle to blow the surface, more surface movement is created that way... if it is flat down, the circular depression created in the area under the fan might not be sufficient to proper move the water surface...

[jiatao]

hmm.. jialat.. okok, i try to change the fan position. hopefully will help.

on another note, rams are quite hard to keep leh, do you feel the same?

thanks for your help though! thank you!

[vinz]

Is your CO2 on a solenoid? If your CO2 is on 24/7 the CO2 levels will build up because it's not being used by the plants. In such a case, CO2 may reach a level that starts to cause CO2 poisoning and cause the fish to start gasping at the surface.

How soon after lights out do the fish start to gasp or surface?

The key here is, are the fish gasping with their mouths touching the surface (i.e. they appear to be sucking air) or they appear to be breathing harder then usual (significant gill movement). If they are just swimming near the surface without appearing abnormal breathing behaviour, then they are fine and probably just prefer to be near the surface during darkness.

Just to be safe, you might want to stop CO2 injection after the lights go off an observe the fish behaviour.

[valice]

on another note, rams are quite hard to keep leh, do you feel the same?

thanks for your help though! thank you!

with good water conditions and diligence in changing water each week, rams are quite easy...

[jiatao]

ok, i think now my rams are stable liao, so now they are not hanging around there in the surface at nite already.

i changed the fan position and now i think things are back to normal le, the fishes that hang around the surface are breathing normally, not gasping for air liao! woohoo!

Thanks all bros for all the kind help!