I welcome lighting advice for my reef tank?

Question

I have had the tank (30g) now for 1 1/2 years. I only have flourescents and need some more power. I was thinking of a power compact 36". However my question is this. If I move up to a 48", can I still use the 36" light and have 6" void on either side? Or if I expand can I buy pot light metal halides to supplement the power compact? I want to be able to expand on a budjet.

Answer 1

Good question.

First let me say that I've used a 24" CF on a 29 gallon tank (30" width), so leaving a "void" at the ends isn't that much of a problem - the light will spread out and light the sides, maybe just not as brightly as the center. You can compensate for this with the placement of the live rock, corals, or anemones it sounds like you might be trying to keep.

Where the difference will matter when you change up to a 48" tank (55, 75, or 90 gallon) will be with tank depth. To keep the same intensity of lighting with your present CF, all the photosynthetic organisms will have to be placed near the top 2/3 portion of the tank to receive the same strength of lighting that they're now accustomed to (you can get new inverts with less light-intensive needs to "fill in" the empty space along the bottom, though). Metal halides will give you better depth, but will produce more heat (leading to higher water temperature, greater evaporation), so this might be an issue for you.

If your tank is fish-only, there should be no problem at all just keeping your current lighting on the new tank. If you wnat to upgrade, I would get a new CF that fits the new tank or a CF/MH combination that fits (where the MH are more centered) - buying individual MH unit(s) and putting the most intense lighting at the end(s) works only if you keep your inverts with the highest light-intensive needs on the end(s) of your tank, but that's another option.

Without knowing more specifically what inverts (if any) you might be trying to keep, this is the best answer that I can provide.

Answer 2

What are you going to keep in the tank???
Fish don't need much light.
Most soft corals don't need much light.
Most LPS (large polyp stony) corals need more light yhan you have.
Most SPS (small polyp stony) corals need tons more light than you have.
Lighting all depends on what you want to keep??????????????????????????????????????????????????????????????????????????????????????????
You may be fine with what you have.