Also, just for the record, are you keeping up with your weekly partial water change? Your tank temperature is steady at 76 F? Are your male guppies are chasing them around non-stop?

This may just be the fishy version of sleeping. After all, they can't very well close their eyes. ;)

When you mentioned fish lying on the "ground," I thumbed through a treatise on the subject from the Fishlopeadia by Mary Bailey and Peter Burgess. Their 2000 Howell Book House publication, more expensive than the other fish health books we’ve mentioned lately, is a very detailed work. While not light reading (have used it to read myself to sleep pretty quickly), it is great for searching out explanations for tricky questions. They are prone to compiling long lists and detailed explanations on a lot of fishy topics.

Those authors offer a truly scary set of possibilities as to why fish would be lying on the tank bottom. If yours behave normally during the day, feed regularly, are not at all hollow in the belly or discolored, they may indeed just be resting.

You wouldn't believe the number of possibilities B & B offer. I don't even want to alarm you, if your guppies are behaving normally, your tank is healthy and maintenance proceeds as it should.

Sometimes we are not quick enough to recognize problems in an aquarium. At other times, we may see problems where there aren't any. :)

If they begin resting on the bottom of the tank during the days, I'll trot out the possibilities from the book. For now, if it isn't broken, let's not fix it.