There is more and more evidence that some galaxies in groups show similar trends to galaxies in clusters, such as redder colours and gas deficiency, highlighting that gas stripping mechanisms are not only important on galaxy cluster scales but also in galaxy groups. The question is though, which mechanisms are important in low density environments? To answer this, we need to identify galaxies with recent or ongoing gas stripping in these environments. A good tool for this are optical-HI scaling relations which make it possible to find galaxies with significantly less HI than an average galaxy of the same type. I derived new, multi wavelength scaling relations by comparing the HI content of galaxies in the HI Parkes All Sky Survey (HIPASS) with optical and near infrared datasets available for southern galaxies. I will present these scaling relations and their application of identifying HI deficient galaxies in low density environments. I will also use these relations for predicting the HI content of galaxies for upcoming large scale surveys such as WALLABY, the ASKAP HI All Sky Survey.