30cm equates to appx. just over 11 inches cube tank.
It is good news that the parents were rehomed. This little guy should move to a new bigger tank when he gets over appx. 4cm. This would also mean 2-3 water changes per week as it gets larger also depending upon other tank stock.
They poop a lot and can foul a tank. As well as a larger tank would be appropriate for this type of fish as they rove around and need room to grow and eat film from glass, wood and rocks all the time.
Welcome to the community!