What filters should I be using

I have the large xp4 unit. I have fresh water tropical fish in a 120 gal. tank. About 30 fish in all, only 4 of them about 8 to 12 inches. the rest are under 4". What filter set up should I be using? It is very confusing with all the options, so I was hoping a pro's input could help me.

A: We always tell people to start with the standard setup. This is good for about 80% of users. Once the tank is setup and maturing you should test the water regularly and note any chages in water quality. We recommend the Freshwater Master Kit by Aquarium Pharmaceuticals. This kit will tell you what tweaks you may need to make to your setup for optimum fish health and clear water. In our experience, for a freshwater setup, the best change you can make is to add more biological filtration. It would not hurt to have two full baskets filled with biological media. This is the best "natural" filtration you have and is much cheaper to use than chemcal filters which must be changed monthly.