Hey,
I also have U. gibba in all of my tanks. It seems to establish by itself and was not introduced on purpose.
When I visited Kuantan all the possible Parosphromenus habitats were coverd with a large growing and yellow flowering Utricularia sp.. I took some, but it did not grow as expected. I don´t think any of the usual aquatic Utricularia do harm fishes.
Best,
Bennie