Q. First, I would like to thank you for answering your e-mails. This is part of what makes your magazine so great. I have just dug out my old 20-gallon and was wondering if I could make it into a mini-reef. I have an undergravel filter with two powerheads hooked to it, although I can also get my Fluval canister filter working if I need to. I have two 15-watt fluorescent tubes for lighting, as well as access to some direct sunlight for maybe two hours a day, and, if needed, a small two-bulb incandescent light. Could I use this setup for some live rock and a couple of corals? Could I also add a small fish or invertebrate? Any reply would be very appreciated. Thank you for your help.
A. Although the size of your tank is no problem, the amount of light you are talking about is. The two 15-watt fluorescents are not enough, and the incandescent lamps are too yellow and would give off too much heat for such a small tank. I would recommend that you retrofit your hood with a pair of very high output fluorescent lamps, preferably a pair of the blended lamps, such as the actinic/white sold by Ultraviolet Resources International. Another option is to purchase a new hood that incorporates the newer U-shaped fluorescent lamps often called power compacts.
You can use your existing filtration, but I would recommend doing away with the undergravel filter and using a small layer (1 inch) of fine coral sand on the bottom. Use the powerheads to add some circulation in the tank itself. You can use the Fluval to filter the water and pass it to a small protein skimmer before allowing it to reenter the aquarium.
For stocking the tank, you can definitely keep live rock and some corals quite easily, and the same goes for fish and small invertebrates, such as shrimp. Your only limits would be the growth rate and final size of the animals in relation to the size of your tank. For this reason, choose organisms that either grow slowly, don’t grow very large or are easily harvested/pruned. Your best bet for corals would be star polyps (Pachyclavularia) and mushroom anemones (Discosoma). You can try some stony corals, such as open brain (Trachyphyllia), which do not extend long sweeper tentacles and would not quickly outgrow your tank.