You can have any fish in a bare bottom tank.
The bumblebee goby, I wouldn't put in to a big tank like that, specially with other fish who are greedy eaters.
They are extremely picky when it comes to food and they are slow to eat. So putting them with quick fish isn't an option imo.
IMO... after keeping a BB goby in a community tank, if we ever got another, I'd keep it in a species only tank, or in a tank with other slow moving non-greedy fish.
I'd also invest in live foods. Bloodworms, brine shrimp, whatever. I'm not exaggerating when I say that they're picky eaters. We started off with 2, and one of them starved b/c it wouldn't eat anything we tryed to give it. The one that survived almost starved twice before we could finally get our hands on frozen bloodworms that it would actually eat.
How long is your 75gal? I'm really not sure if 75 is big enough for clown loaches. They're slow growers once they reach a certain size (around 4-5 inches), but people often aren't able to provide a larger tank when the time comes. So might be best not to get some? *shrugs* It's up to you though of course.
You can def keep clowns and tiger barbs together. Mine often school together since they look similar to eachother. It's pretty cute lol.
With tiger barbs. The more the better. Sometimes you can get lucky and 6 will be fine w/ no nipping, but the more there are, and the more room they have in a tank, the less nippy and aggressive they'll be.
So IMO.. at the very least, get 6-8 tiger barbs.
Clown loaches are shoaling fish as well, so at the very very least, 4.. but I'd aim for 6.
