Aquarium photography is kind of difficult with point and shoot cameras. The problem is that you have a flash on the front; you are not able to direct the flash to "bounce" off of anything. So naturally, when you are shooting into glass, you will get a reflection.
But it definitely is do-able. When I use mine, I tend to use the max zoom setting, so that if there is a flash glare, there's a chance you won't be able to see it in the final picture. If I don't zoom, I tend to hold the camera right up to the glass, as long as the fish are far enough back to be in focus. Also, if your aquarium lights are bright enough, you may not need a flash.
The other problem is that digital cameras have this horrible curse called "shutter lag". Basically what this means is that you will click down on the shutter button, and maybe a second later, the picture will actually take. Really frustrating when trying to shoot fish, but it is just a problem you have to deal with when using a point and shoot digital.
So here are my suggestions:
The Canon A95 is a really good all around point and shoot digi camera. You tend to find it for just over $300, but Canon is offering a gift card right now with purchase (I think it's for $30). http://consumer.usa.canon.com/ir/controller?act=ModelDetailAct&fcategoryid=145&modelid=10468
I have used this camera and think it is probably the best for that price range. It does still have shutter lag, but not nearly as much as others. The photo salesmen at my work absolutely love it for a digital point and shoot. It takes compact flash for the media (basically a ?disk? that you save you pictures to), which is very durable - I remember once, when printing a customers pictures from a compact flash, that my co-worker "lost" it - we found it an hour later in her glass of water! We let it dry for a day, and it worked perfect the next day! (shhh? don?t tell the customer!) It also is a 5 megapixel camera - which means it will be fine for prints up to 5x7.
I inquired to my co-workers about cameras that have less shutter-lag, and the Casio Z40 was suggested:http://www.steves-digicams.com/2004_reviews/ex-z40.html
I have not used this camera. A problem that I can see is that it takes "sd cards" for media. I won't go into what an "sd card" is, but I have found them in the past to be very unstable. So it would be a type of media that you would have to be very, very protective over. This camera is a 4 megapixel, good for prints up to 4x6.
Overall, after reading some reviews on the Casio, I would spend a little extra and go with the Canon. It's a very nice little camera. Google both of them, and see which on matches you better.