If you have nitrite, you had ammonia, and unfortunately that will kill the fish. Nitrite is bad for fish. First off, I would make sure your tank is fully cycled prior to adding anything else. There are many threads here to help you figure that out in a method that works for you.
Next, I would reconsider your inhabitants. A 13.5g will not support a diamond goby or sand star for long. Look at little gobies, maybe a small blenny. But not until you are sure your tank cycled.
Good luck. I hope you can get the tank stable and mature as they are a fun size tank, but need to be very careful to keep stable.
Next, I would reconsider your inhabitants. A 13.5g will not support a diamond goby or sand star for long. Look at little gobies, maybe a small blenny. But not until you are sure your tank cycled.
Good luck. I hope you can get the tank stable and mature as they are a fun size tank, but need to be very careful to keep stable.