Undergravel filters are a little out of date, but they used to provide good filtration and still do. They tend to be used in reverse now, so rather than pulling water down through the substrate they move water up through it so detritus goes back into the main body of water where a second filter (like a
HOB) can pick up and filter out this detritus.
So your set up will work fine if that's how you want to go. I would go with gravel rather than sand though.
In my opinion, if one filter provides sufficient filtration and cycles the tank, adding another filter wont cycle it more. It will give you redundancy though should 1 filter fail. If you are using a
UGF in reverse, that second filter will provide some needed mechanical filtration. The
HOB can also be used for some chemical media should it be needed.
Linear Mode
