A light with focus on lots of blue would be my best recommendation. I have had great success with Kessil.
I'd like to say magnesium is pretty important for these guys. They are also quick growers in my opinion and will take up calcium and carbonates (kh
) from the water quickly in a 20g environment as they grow their hard skeleton.. (As you see more growth do more water changes haha)
Luckily for you the practice of 5-10g water changes weekly is actually a good way to restore elements in a balance ratio. The use of salts with higher kh
, and mg
would be of benefit to you. Such as the Instant Ocean Reef Crystals version. You could also use, for example, Instant Ocean Regular Salt Mix and dose your calcium, alkalinity, and magnesium all in dry powder forms both during watcher changes and during the middle of the week. Should you choose to skip a water change or do a smaller change than normal (say 5g instead of 10g) just dose these elements slightly more significantly.
I also can't blindly tell you to dose without encouraging you to get a test kit for these elements. Red Sea has a good one. However, you would surely be safe with just 1 or 2 doses of all 3 elements (come on don't prove me wrong and dump way too much for how much coral you have
) I mentioned without testing if not just for the continued growth of coralline algae. Corals would prefer the stability achieved from more frequent smaller, ideally daily, doses of elements.