i think elephant noses are bottom feeders. you can feed them shrimp pellets, bloodworms, tubifex worms. how big if your tank btw? elephant noses get pretty big.
Elephantnoses can be out competed for food with quicker moving fish such as tetras etc, but if you feed frozen/live foods such as bloodworms, brineshrimp etc right after you turn out the lights they'll have a better chance at getting their fill. Over time, the elephantnose will venture out while the lights on and start to feed during the day.
Make sure you have plenty of hideouts and ideally a soft sandy substrate instead of gravel....the gravel can damage their sensitive nose.
They are VERY sensitive to water quality like Roan said and are expert jumpers, so make sure the tank is covered well! I lost my first 2 to carpet surfing....you'd be amazed at how small of an opening they can get through
I would say a minimum of a 75 gallon for one of these fish is required as they can reach up to 10 inches.