I just purchased a FX5. From all the research I did it seemed like endless possibilities. At the end of the day, I took the simple route of buying 6 boxes of biomax and only using that. I also purchased the polishing pads and the blue pads which I plan on only using periodically as it is needed.
Some advice. I have used hang on the back filters (specifically emperor 350,400) for 13 years. The FX5 is my first cannister. I went with the fx5 because of quietness and positive reviews I found everywhere, but I will tell you it is a pain to clean this filter. I have had multiple issues setting up my new tank which has required me to open the FX5 multiple times. This is not an easy task. Also, I consistently get air trapped in the filter so it makes lots of noise which takes time to get out. I cannot yet talk to the effectiveness of the filter, but I will tell you that from a convenience perspective this filter is a pain.
try putting vasoline on the lid o ring, ya should never have any air get in when the unit runs unless it from when you service it and if ya do it blows all the air out within 2-5 mins ..... i never have micro bubbles anymore never get noise from it, mine run great and ive never had a issue at all i think there great IMO
ps AS A MATTER OF HOW MANY PADS ...maybe 2-3 would do