You have a decision to make between ease of use and flexibility. If you want to take really good shots consistently, you can't do it with anything but a interchangeable lens camera. If you want convenience, and you want to be able to chronicle your tank's development or snapshot some coral a compact camera will do fine.
If you want to take pictures of small frags with great detail and minimal noise, that means you will want a macro lens, which is what you should be looking at alongside each camera (some companies have better lenses, or better suited lenses). Are you willing to take out your tripod and do very long photo sessions every single time, or would you want to be able to take pictures on demand, handheld? For me that was a huge selling point of companies that offer in-body image stabilization, my hands are shakier than most and with my Canon I could never do any handheld work. Now I can take high quality pictures without taking out my geared tripod and macro focusing rail.
If you need the image stabilization, that leaves you with Sony or Olympus, or the alternative of buying very expensive stabilized lenses. Personally, I would recommend a mirrorless camera with in-body stabilization. You can attach any lens to it (and it will be stabilized), which gives you a wide array of options for choosing lenses.
