Goldfish are the Rodney Dangerfields of the aquarium world.

If you want to decorate your goldfish tank, stick with pea gravel. Popular but ill-advised alternatives include driftwood, which gives off tannic acid, and colored gravels, which not only leach out dyes, but present a choking hazard.

When Jo Ann Burke of Semmes, Ala., started keeping these hardy little fish in 1976, and even when she started importing fancy specimens from China a decade later, no one diagnosed goldfish. No one could tell her what it meant when a goldfish yawns (oxygen deprivation, perhaps) or when it has white eye flecks (brain flukes – yikes).

So in the early 1990s, this mother of eight enrolled at the University of Florida at Gainesville to do graduate-level coursework that led to her certification in the diagnosis and treatment of freshwater fish disease.

Based on that scientific grounding – as well as trial and error amid the 8,500 gallons of aquaria that filled her home – she pioneered ideas such as the 3 percent salt dip: putting a newcomer in a solution of 2 cups rock salt (never table salt) to 5 gallons tank water.

“You put them in for one to five minutes, and when they belly up, it means they’re done,” she says matter-of-factly. The salt dip purges the fish’s system and removes parasites and bacteria from its protective slime coat. “When I first started suggesting it, people thought I was off my rocker.”

Today, on goldfish chat lists and e-mail discussion groups, the name Jo Ann Burke is typed with universal reverence. Newbies are counseled to read her online instructions for giving a three-point goldfish physical, or directed to her “Anatomy of Goldfish Poops.”

These days, the self-proclaimed “Goldfish Guru” is semiretired, with just three ponds of koi on her country property. Replacing her tanks are antiques, and she sells high-end pottery and glass on eBay.

But Burke still fields countless questions about these popular little fish, helping distraught owners sort through symptoms as perplexing as bubble eating and tail standing, black-streaked fins and protruding anal ports.

“I just want people to have the ability and knowledge to care for these absolutely wonderful creatures,” says this down-to-earth, native Vermonter, who has had goldfish live to 14 years, and koi more than twice as long. “Most of the people who call me can’t spell pH. So it’s like, ‘Look at his butt and tell me what you’re seeing.”‘

One myth she’d like to debunk right here, right now, is that goldfish are dirty. “If people do regular tank maintenance and they have proper filtration, they will not have dirty tanks,” she says.

Prevention, of course, is key. Because goldfish just can’t say no to seconds – or thirds, or fourths – “only feed once a day, in the evening, and no more than they can eat in three minutes,” she says. “A hungry goldfish is a happy goldfish.”

Invest in a solid-flake food that sinks “so the fish are not gasping at the top of the tank,” Burke recommends. Look for a protein content of 37 percent or better, and stay away from corn-based foods.

Other no-nos: Decorating your tank with driftwood, which gives off tannic acid, and colored gravels, which not only leach out dyes, but present a choking hazard. Stick with pea gravel instead.

“The biggest mistake people make is they dump the new fish and the water it came with right into the tank,” Burke continues in exasperation. All this does is introduce whatever diseases were floating around in the fish’s previous tank into your pristine little kingdom.

Instead, float the bagged fish in your tank until the water temperatures are equalized, gently lift the fish out, give him the aforementioned salt dip, and then place him, sans water, in the tank.