A nice liquid to consider is a court bouillon. Because the poaching liquid gains flavor from the food, you can use part of it to make a sauce. Or save it for soups. You don't have to buy a big copper fish poacher. Use a skillet or saucepan large enough to hold both food and enough liquid to cover it.
Woks work well.
Try to use the smallest pan that will hold the fish and the liquid. If you use too big a pan, the amount of liquid you'll need to cover the fish will dilute the flavors. Don't put a lid on the pan while you're poaching. Broiling is 'under' appreciated art Broiling works especially well with stronger-fleshed fish. Broiling is also a natural choice for other meats and hardier vegetables.