The Light Keeps Going Off In My Fishtank.

The chaps, pictured in one of their fleetingly enlightened times.


I know the title of this post sounds like a country and western song but that's just a coincidence. The light really does keep going off in my fishtank - well, one of the tanks, anyway.
Not a big problem, you might think? It could be. I'm worried about the consequences. You see fishies are strange coves. They kinda live their lives around lightness and darkness - much more so than we do. To a fish, inky black means no more "Ooh, here's a glass wall! Ooh, fancy that, here's another glass wall!! Ooh, this glass wall wasn't here yesterday, I'd swear?" It also means it's piscine bobos time. Light, on the other hand, means it's time again to meet the other fish in the tank you are certain weren't there yesterday, to have a bit of a swim and then look forward to dinner. Muck around with these divisions and you're asking for a tropical storm.
The trouble with the light being on the blink - literally - is that it's confusing the chaps no end. No sooner have they stretched their fins to supposedly greet a new swimming day than "ping!" - it's time for bed again. Then, just when they've got their Jaws jimmy jams on, the photo alarm goes off and they've got to get up again. I'm not sure if it's possible for fish to have nervous breakdowns but I'm sure mine are heading that way.
I've bought no end of bulbs and transformery/switch thingies but I can't seem to solve the problem. I'm damned if I'm going to splash out more - my local fish doctor is already a millionaire thanks to me. So, I'm on the lookout for suggestions.
Anyway, I'm going out for a beer with my chums now but, in the meantime, all help will be gratefully received. Try not to worry too much about it, though.