"We have fish, and water." The original pitch for St Kilda's grungy, eccentric and excellent seafood establishment when owner Renan Goksin​ opened in 1998 was perhaps modest, but it was true. Long before Melbourne became obsessed with katsu sando shops, pasta bars and other singularly-focused operations, Claypots was pioneering an extremely minimalist seafood vision on Barkly Street in St Kilda.

The process was this. In the morning, Goskin went to the market and gathered fish to fill a cabinet. In the evening, St Kilda's gig hags and backpackers came to stack the bare bones tables in the tiny front room, with their own bottles of plonk in tow. There were no toilets, no bookings and no cards. You waited for tables at the Village Belle. If you forgot cash, you had a week's grace to pay.

The whole operation – according to manager Vivienne Guy, who still co-captains the good ship St Kilda in her cowboy boots – was "loose".

Chances are, it still would be but for steadying heads and hands like those of now-owner Neelam Sami. Sami, Fijian-Indian by birth, was hired in 1998 as a daytime cook when her Australian husband claimed, with misplaced confidence, that he could make thalis for day trade. Failing, he brought Sami in to show him what to do. Goskin saw, gave Sami a job, sacked her husband, and eventually conquered the night trade.

"No one showed up for the night shift and I just prayed no one ordered the calamari – the one grilled dish I didn't know how to do," says Sami. It was the first order. "When I had made that, I decided. I will own this place now." In 2016, Goskin gave her full control.

At 21 this year, Claypots – which had a branch on Gertrude Street in the early noughties and still stars at South Melbourne Market plus two nipped-and-tucked branches under the name of Claypots Barbarossa in the CBD – isn't as old as some Melbourne icons. But it is the most faithfully preserved slice of what St Kilda once stood for in its grungy heyday.

The facade is a Rubix cube of panes framed in different colours. The concrete floors aren't polished by modish design, but a million soft-shod feet. Every inch of space reflects the bizarre boho artistry that was once St Kilda's calling card: red bar stools with metal dragons coiling up their spines; a playful model tram chugging back and forth across the doorway; folksy band posters pushing magic Sundays in the courtyards. The poem around the door, written in Phoenician alphabet, is impressed in clay mixed with all the spices used in the restaurant.

The menu? There's the cabinet of daily catch. Or the blackboards. These list the eponymous claypot creations (Creole gumbos, Moroccan stews stuffed with mussels, or diamond clams and prawns French-style with red wine rouille and fried bread) and a list of fish that (might) have rolled in – and what you could have done to them.

But it's more a mood board: serving suggestions that regulars ignore. One group of eight that has been coming every Friday for 19 years refuses to converse with a waitress and goes straight for the kitchen with orders "their way".

For visiting mortals it's flatheads and flounders, snappers and stingrays: grilled, fried or braised – but always whole, arriving on big shared platters for sticky-fingered dismemberment with cheeks of lemon, batch-baked potatoes (or sticky rice for the big 3kg fish) and steamed bok choy licked with a little chilli jam. It's been this way for almost the whole of Claypots' existence and nothing is going to change.

Why should it? There will always be more restaurants in Melbourne. Where else can you smash a crab in a sunny courtyard, bathed in the spirit of St Kilda past? Only Claypots. Still a big fish of the seafood scene.

Est. 1998

Signature dishes Chilli crab, sambal stingray, cajun flathead, garlic king prawns.

Famous diners Sydney Swans players, Kristian Nairn (who plays Game of Thrones' Hodor), Dannii Minogue. Two Underbelly actors worked here but were ousted for pulling in fans, not punters.