One of the problems with aquarium lighting is it's not a very natural color, and the way our minds compensate for this in ways our cameras do not. I've tried setting the "correct" white balance, and in my opinion, this does not always yield the truest color. Now, I simply shoot in RAW and adjust the white balance manually in my RAW editor. I know how the corals look to me, and I simply use the sliders to approximate my interpretation of what I see in the tank. It takes some practice, but before long, it only takes 10-20 seconds per image. Playing devil's advocate to myself, the downside is that it is subjective. Let's say for example you're taking pictures to sell your corals online. In this case, using a white balance card may be a better option. So I'll talk to that for a moment:
First, if you don't have a white balance card (and a waterproof one at that), any relatively pure white object will do. The lid of a white 5g bucket for instance. Once you've got that, make sure the object is under water. You need it reflecting the same light that is hitting the subject of your photos (i.e. your aquarium lights). Hold this object at about a 20-45 degree angle from vertical. This will make sure it's reflecting the aquarium lights. If you're setting the white balance in the camera, make sure the card is filling up the majority of the frame (I can never remember exactly how much it needs) and there are no shadows on the card. If you're going to adjust the balance in PP, you just need a decent sized area that's free of shadows, so far more leeway there. Also, if you're going to fix it in post, shooting in RAW is highly encouraged. The compressed formats drop a lot of the color information, and adjusting the white balance of a JPEG can result in noise, color distortion, etc. In RAW, you have none of these issues.
As I write this, I realize there may be one other issue here. Shooting under different color lights can be extremely problematic. The blue LED may be spotlighting one coral with all of its blueness, while another area of the tank is getting all or mostly all of its illumination from your much less blue lights. If playing with the white balance is not enough to make all areas of the tank look correct, you may have to use to versions of your image with different white balance and blend them together in Photoshop or some other editing program.
