Join Date: Jan 2004
Location: West Chester, PA
I recently bought a Canon Ditigal Rebel SLR, and an EF 100mm f/2.8 Macro USM lens (canon). I don't know the specifics of your camera, but I can give the following advice.
If you want the subject(s) to be in focus and looking good, you're going to need a decent low-light lens and you will want to crank your aperature nice and tight. I go with an f-number of between 9-20 depending on what I'm shooting. This is with my macro lens though, which is a lot more sensitive (up close) to focus-range issues.
In order to use a tighter aperature, you're going to need a TON of light on the tank, or you need to leave the shutter open forever. I currently use my flash in addition to 360w of overhead tank lighting. This isn't really the best way to do it. From what I've read, the best way to go about this is to build an overhead flash canopy and use a remote flash on top of the tank. This way you have natural top-down lighting on the plants and fish, and avoid glass-reflection issues, as well as unnatural looking shadows. With a regular camera flash, you end up with tons of problems if the flash hits the glass and reflects back into the lens or even if it illuminates the room behind you, which reflects on the the surface glass. You want everything else in the room off, and the glass perfectly clean, etc.
Another issue is ISO and shutter speed. If you're taking pics of a planted tank with no fish, or if you don't care that they're a blur, you can ignore the flash issues and set your camera for a long shutter opening. I have done this with my camera on a tripod and a delay set so that you don't wiggle the camera when pushing the shutter button. You may be able to get a remote camera control too, though I don't know specifics on the Nikon.
As for ISO, you should try to shoot for the lowest possible ISO setting on a digital camera, since this will be the "native" mode for your CCD chip. Anything above the lowest ISO setting will introduce noise, which is a result of the increase in gain on the signal coming from the chip. The noise is likely not noticable though until higher settings. My Canon camera shows a little noise at ISO 1600, but lower than that I cannot tell. If you want to test it, I suggest taking identical photos of something which has a pure-black area (shadow or black color). Compare the shadow/black areas on each photo. This is where the noise will be most evident.
I hope this was helpful.. I am new to this as well, and currently looking into an overhead remote flash system. I'll let you all know what I end up doing.