sand and gravel?

I'm going to say no, because if you look at the top of the undergravel filter, you'll see that the holes are pretty large and all the sand would eventually get sucked up and filter out. I assume most of the sand would just be sucked up and blown back out into the tank which would be quite messy. So unless you could cover those holes, I don't think it is possible.
 
here you go

if you already have gravel in your tank, that "sand trap" idea is cool. But now that i have a banjo, i wish i would have made it all sand.

anyway, check these pics out (dont know how to put more than one on the same reply)

* he still has a little sand on him, he just came out to eat. if you want one ill try to get a pic of him burrowed tomorow...

banjo3.jpg
 
1 more

i tried to get one of him out of the sand, but it was so blurry you wouldnt be able to tell where it was. i suck at photography.

banjo1.jpg
 
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