Yes, they were taken with Rogger's Nikon Coolpix 995 which is an older camera. These cameras are well known for their macro ability. They were shot without any additional lenses on the camera too!
As far as lenses for the Rebel, I know that Canon makes some excellent macro versions. There are also add-on macro adapters that you can put on other lenses. Since I'm not too familiar with these, I can't make any specific recommendations. Your best bet might be to take your camera to a store that sells a variety of lenses for your camera and try them out. Try focusing on something that you think is the size and distance you would be shooting at in your tank and go from there.
And the ricordeas are beautiful...the photos are not retouched...that's exactly the coloration they have!