At the face value this is wacky. It sounds like it shouldn't be.
The only thing I can think of is that when a light is turned off, the oxygen production by the plants ceases and now plants consume oxygen, depleting the dissolved oxygen. Hence, the catfish are trying to escape the suffocating water.
Plants, as all living things, consume oxygen at all times, it's just that they produce 100x more than consume in the day light.
--- Was there an adequate aeration in the tank to keep the water adequately aerated in the night time?
--- Have you noticed a delay in the catfish behavior? I mean it would take some time, maybe 30 min to a few hours for water to get oxygen depleted once the light's off.
I understand it does not explain why they are ok with a tiny bit of a night light but I'm at a total loss as to why else the pictus would do this.
Fish jump out of the water to physically shake off parasites, but this shouldn't depend on the amount of light. So this explanation doesn't appear to fit.
Other things may make fish behave unreasonably like that, e.g. a sudden pH swing or temp, etc. but this doesn't usually involve light either.
Anyhow, planted tanks are not my experience. Never had them. So maybe people who had them would have better things to propose.
The only thing I can think of is that when a light is turned off, the oxygen production by the plants ceases and now plants consume oxygen, depleting the dissolved oxygen. Hence, the catfish are trying to escape the suffocating water.
Plants, as all living things, consume oxygen at all times, it's just that they produce 100x more than consume in the day light.
--- Was there an adequate aeration in the tank to keep the water adequately aerated in the night time?
--- Have you noticed a delay in the catfish behavior? I mean it would take some time, maybe 30 min to a few hours for water to get oxygen depleted once the light's off.
I understand it does not explain why they are ok with a tiny bit of a night light but I'm at a total loss as to why else the pictus would do this.
Fish jump out of the water to physically shake off parasites, but this shouldn't depend on the amount of light. So this explanation doesn't appear to fit.
Other things may make fish behave unreasonably like that, e.g. a sudden pH swing or temp, etc. but this doesn't usually involve light either.
Anyhow, planted tanks are not my experience. Never had them. So maybe people who had them would have better things to propose.
