My father and I have used undergrounds with powerheads for a long time but the guy we talked to at our LFS said it is not good enough and we need to get a Canister. Not sure how much better it is or If he is just trying to sell us stuff
Hello; I submit that you have the experience already to help with a decision. I have used the ugf's myself for many decades.
A few things come to mind. One is that there are a number of folks that are against the UGF regardless of the success they have had in tanks for a long time. Some are against them and are often vocal about it. I also have an area fish shop operator who is negative about them. He will not stock them. They are considered old school and that seems to be the main argument I have found. I wonder if glass will someday be considered old school?
Another thing is the expense of a canister and the operating procedures. I have not run one yet myself, but have read many threads discussing problems with setting them up keeping them going. With any piece of equipment the procedures will have to be learned to run it properly. You may wish to search threads about what is involved with a canister.
I agree that doing a substrate vac from time to time and some sort of secondary filtration such as a HOB should be used with a UGF. The argument that a UGF does not remove detritus misses the point that they are not designed to remove detritus. For that matter I have found that doing a gravel vac is needed with any filtration system I have ever used.
The single biggest issue in my mind probably being the cost of a canister vs. the UGf you already own. I imagine one or two HOB's for mechanical filtration may be less expensive.
Good luck