Need light, well that depends on what you mean by "need". In many catfish, they can see quite well in almost complete darkness, so they don't need light for that purpose. Not all tho'.
However, if you want to see what's going on in the tank, YOU may want to have sort of light on it...
There are of course exceptions, and most don't mind some light, as long as they have some decent hiding places.
Of course, before we've identified your fish, it's near impossible to be specific about it's requirements.
The reasons I suggested for why it's inactive are just SOME of the possible reasons. And with a risk of repeating myself, it's terribly hard to say WHY, without knowing what fish it is. Some fish needs to be in groups, others are best kept alone. Some are by nature very inactive, others are very active. If you have one that is by nature inactive, then it's behaviour may be perfectly normal. If it's naturally very active, it's not normal behaviour. I can't really say until we get it identified at least to a group of fish.
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Mats