Fish. We watch them to feel better about ourselves. They help us to relax, to unwind, and generally to remember that however bad life might be, at least we're not swimming around in a one foot cube sucking up other folk's poop twenty-four hours a day. A real aquarium is quite a hassle to look after, mind you, so there's definitely a case to be made for the virtual variety.

This PC-based aquarium screen-saver is now in its fourth incarnation (though we can't say we've seen the previous versions). Once installed, it automatically sets itself up as your default saver, although you can run it any time you want by clicking on the desktop icon. And once run, naturally, you're presented with a shoal of screen-saving fish.

And a load of options to tweak which alter the appearance of your tank. You can select from four different backgrounds - three of which are coral-based, and one which is a plain sand bed - and there are over forty types of fish to populate it with. If you want, you can choose a random selection of fish and cycle the tank backgrounds on a timer for variety's sake.

The graphics are very impressive, boasting some pleasant lighting effects along with well drawn and animated fish. Some exotic and brightly coloured species are included, such as the luminous pink "square spot fairy basslet" and glowing green "moon wrasse." There's also a bubble effect (from the virtual air pump) which can be adjusted in terms of its position and intensity, but it makes a rather irritating noise that isn't particularly relaxing.

Fortunately you can turn the volume down on this, or mute it entirely and replace it with some music. There's the facility to import all common audio formats and you can build a playlist, then use the shuffle function to create a jukebox for your screen-saver (as long as you can find some tunes with a chilled enough ambience).

In terms of interaction with the fish, the two obvious options are employed. You can (virtually) tap on the glass and see the fish react - slightly nervously, but then you probably would too if the jolly pink giant was clattering on your windows with his pudgy digit. Or you can feed them and watch the flakes swirl towards the bottom of the tank while the fish scurry about trying to catch them.

And that's pretty much it really. The program can also be run as an active desktop and if you have multiple displays, there's a setting that allows your aquarium to be stretched over up to three monitors. It's a little disappointing that there are only a few different tank backgrounds and no facility to customise the landscape and get really creative, but this is a reasonable "Ronseal" program (i.e. it does what it says on the tin).

PC Aquarium Deluxe 4 is relaxing and pleasant to watch, with some smartly rendered, life-like fish. However, the option set is fairly basic and it's a shame the developers couldn't have made the aquarium a bit more customisable. Still, it's a solid enough effort.