Do the cheap slave flashes work just as well as the more exensive ones?

I'm young and chronically ill, so I can't get a job. I spend all my money on my 5 fish tanks… I have huge fish, they're not cheap to feed.
I've gotten into photography recently and want to get pictures of my fish, but the pictures I get don't turn out too well. I need a slave flash to put on top of the tank to get better lighting during a picture - it's what a lot of good fish photographers do.
However I don't have the money to go buy one of those extremely expensive ones. I have a Nikon D50, can anyone point me towards the cheapest slave flash that would work for what I need? Is there anything else I would need to go with it to make it work?

Hehe, thanks for the help guys. I'm new at this photography thing.

For what you are talking about, a small inexpensive slave flash should work just fine - the distance is small. The most likely problem with buying cheap is uneven coverage and perhaps some inconsistency of timing if you were using more than one.

If you can continuously illuminate the tank bright enough from above and forget flash might be the better way to go. Then you can photograph your fish as you would any other subject. What you want to avoid is as little of the light falling directly onto the pane of glass your shooting through as possible as that will just flare and reduce contrast or even just 'white out' the image. In other words you just want the light from inside the tank, all other room lights should be turned off otherwise you will see reflection od objects inside the room.

This is the lighting system used in every Aquarium I've ever been to, even to the point of painting the area the customers are in matt black to avoid reflections.

Place your camera lens flush with the tank (this will reduce any reflections)

You can use any flash that has a slave feature and use the flash on your D50 to trigger it.

Look on page 54 to see how to adjust the on-board flash to maybe 1/2 power, letting the slave flash provide the key light.

You will have to experiment with your lenses aperture to to get the correct exposure.

Most definitely not. Build quality is lower and flash cycles are fewer. Worse compatibility is poorer so if you depend on TTL, don't. If you are willing to shoot manually then any $50 flash will do.

http://keerok-photography.blogspot.com/2012/08/how-to-use-generic-flash.html

If you are chronically ill, you spend your money on maintenance medicine, not on 5 fish tanks.