it could be, it is always best to have at least two animals from one kind in a tank(there are exeptions)
NO, it is a solitary animal and that's what it likes to do.
Catfish eat using there mouth. Most are bottom feeders. They usually gulp or suck in gravel, take everything they want off it and spit out the gravel.
Catfish... aren't picky in the slightest. It wound be like asking a pig if it would rather live on a farm or an orchard. You can have a bare-bottom tank and they will be happy. As long as there bellies are full, it doesn't matter. but keep in mind. Large catfish LITERALLY inhale their food. So if you have large catfish, it be best to have gravel to prevent choking.
I have two Bristlenose catfish and they are doing a great job of keeping the tank crystal clean. I would definitely recommend these.
from your description it sounds like a DOJO loach or WEATHER loach.
Catfish find their food overwhelmingly by smell - they have very poor eyesight. When fishing for catfish, the most foul smelling, disgusting bait you can come up with will give you the best results, as a rule.
filters only filter the water they don't clean the walls of the tank or the gravel in your tank. you still need to move rocks and plants to get to the crap left behind that the filter cant get. you should do this when you clean your filter. depending on what sort of fish you have they can clean the tank for you cichlids will definitely clean the gravel for you as they build nests like birds and are always sucking up rocks. you should try to get a catfish as these are bottom feeders and they will stir the water up for you as well. you can get some catfish that will go good with goldfish as well.
Nice clean sand that is meant for an aquarium. Be sure not to get saltwater sand for a freshwater aquarium. The reason sand is best is that (1) unlike gravel, it does not have anyplace for uneaten food to hide. Uneaten food is the number one polluter of aquariums, and pollution causes disease. (2) Some fish are sensitive to the rough edges of gravel, and some of them even become damaged by it -- such as certain loaches and catfish, whose barbels get scraped up by it. People keep buying gravel though just because of the cosmetic effect. I'd suggest getting some nice, fine-grained, soft white sand. It makes a great background for any color of aquarium furniture.
The gravel shrivels up because of the acid.
Yes because you can still see the gravel inside the water
If your Cory catfish is in a tank with no other fish species, it really doesn't matter. If you have other fish species with it in a tank I would try turning off the lights at night and feeding your Cory then. It will give your Cory a better chance of getting the food before another fish gets it because corys don't use their eyes to find food, they use their barbles.
When driving on gravel you can lose control of your car because the gravel is so loose. The best way to drive on gravel is to go slow.
Yes, gravel is naturally occuring in riverbeds (because of weathering and erosion.), and special gravel pits.