Tubastrea corals don't require light, but also don't need low light. They DO NEED high flow, to bring food their way. The mistake most people make is putting them in a low light area. Due to how are tanks are typically aquascaped, low light usually also means low flow, since it's usually blocked by rocks. Low light usually also means an area that's inconvenient to reach, for feeding purposes. Put it in the most convenient spot for you to reach, so you'll be more likely to feed it more often.
Each polyp needs to receive food. I'd suggest trying frozen Cyclopeeze. There's a few different ways to target feed Tubastrea.
1. Remove the coral, putting it in a container with a food slurry, for about 30 minutes. DON'T forget about it, it really stinks when you find it a couple days later. Don't ask me how I know this, but I DO!
2. Use a 1 or 2 liter bottle, cut the bottom off of it. You can place it over the coral and squirt food into the mouth piece, with a turkey baster. This will keep shrimp from robbing the food. Feeding Tubastrea, in a tank with shrimp, is difficult!
3. Train it to extend it's polyps when you want it to! This requires feeding it, at the same time of day for awhile, until it "learns." Start with the "juice" to get it to extend it's polyps and then squirt the food into the extended polyps.
Remember, they don't need light but also CAN be kept in high light. They NEED high flow.
