Freshwater ?

Ive had freshwater a few times, they are totally harmless to fish,when my kribensis had babies the parents use to let them swim round the and neither were bothered. you don't need to feed them special food as they eat fish flakes or basically any food that finds its way on the bottom(even dead fish) , i use to drop a sinking fish pellet in every day,they love them. just make sure they have a way of getting out the water otherwise they will die after a few month and make sure they don't escape out of your tank because they will.