If your Oranda is still pooing it is unlikely to be constipated, you might want to consider changing its food. However if you still think it is constipated please read on.
This might not be a recognised remedy but I have been keeping and breeding goldfish for about 25 years now.
when i was young I had an Oranda that was clearly constipated. It was all black and swollen at its back end.
I put it into a seperate bowl without an air pump so it had to come to the top of the bowl for air, and added a couple of drops of Codliver Oil.
The poor wee thing ended up doing a poo that was about a mile long, it covered the entire bottom of the bowl.
The wee fish went on to live a happy life for about 7 years after that.