BioHome Ultra is the go to Bakki shower media for professionals, it is the only media that we know of that can properly colonise anaerobic bacteria, which are key for full cycle filtration
The main difference is that PU cannot cure in wet conditions and MS Polymer sealants can, MS Polymer is also fish safe out of the tube before curing so is perfect for repairs when fish cannot be removed.
Both have excellent adhesion properties and are fish safe once cured