I know -- I'd imagine that many of you pros consider the house brand Top Fin from Petsmart to be garbage... ...so forgive me in advance..

I bought one of these:

Top Fin&#0174 Premium Undergravel Filter - Filters - Fish - PetSmart


I have what I believe you folks call a HOB filter now, that hangs on the back of the tank and has a tube that sticks down into the tank.

My idea was to simply extend that tube down to the gravel level so that it'd do a better job of picking things up from the top of the gravel field.

The store salesperson said the undergravel was a better way to do it-
I pointed out the filter that I had on their shelf, and he said he thought that would work, but didn't know how to hook it up (said their website had directions, that was certainly wrong...)

I see references in other threads to "power heads" and air lines, etc.

I did get an air pump for a 10gal tank (they were out of 20gal), and some line,
and I was thinking maybe the method here is that the undergravel filter hooks up to that tube on my back-of-tank filter??

I don't really want to open up the undergravel filter in case I've gone the wrong direction and need to return it...

Any clues folks?

I only have one undergravel filter in one of my tanks and that is a 90 gal. I made it myself. I use 2 powerheads on it, but I also have 2 hobs as its a cichlid tank.

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Take it back. Its not going to clean your bottom any better. Use a gravel vac to clean the bottom when you do water changes

My 2 cents

So is it better to replace the intake tube on the existing HOB with something longer/better in some way, and to improve the circulation in the tank?

I added a volcano with an air stone in it -- the kids love that!

So my water should be circulating better now - but it still seems like that little tiny tube that's only 4" down in the water and only has 1" of openings isn't exactly going to be in the path of all the stuff in the water that should be filtered out.

Seems like there should be something that's got more surface area to take up water and crud to head into the filter..

No, just extend it all the way down, it should work fine. The gravel vac will get anything else with water changes.