You may also add Iodine, my rainbow welso coral was doing great for a few months. Then I made the mistake and added sand and through my tank into a mini cycle. It took two months to figure out it needed iodine. It took one drop per 25 gallons and oh what a difference it made. I understand its in the salt, however in a 29 bio cube there's not that much and everything uses it. Give it a try. You should notice something in a few days. Also, get a lfs
to check your water. Always helps to have someone else check.