The story of LEGO 10366 Tropical Aquarium's versatile new piece

LEGO 10366 Tropical Aquarium has a new piece that's already proving to be one of the most versatile yet, and it's only been used for fish so far.

We're just under a month away from the release of the huge 10366 Tropical Aquarium, and official images have revealed that it introduces a new element to the portfolio, featured in many colours in the new LEGO Icons model. It's used for various parts of the fish in the set, but its shape lends itself to many other uses beyond animals.

The story and reason behind this new piece's debut has been shared thanks to the design team, including why it's already proving to be one of the most versatile elements yet.

"When you design cars, you don't often get to pick glittery purple and colours like that to use, and all the other interesting elements," said designer Sven Franic at LEGO Fan Media Days 2025.

"So it's really something that we had to test the shapes and colours of the LEGO system. I have Matteo, our element designer, with me. There was one difficult shape to recreate, which was the fins of the fish, and Matteo can tell you more about that element."

As varied as fish's fins can be, the designers devised an overall shape that the new element could take the form of to resemble the most important aspects of various fins. The element, seen at the back of the striped brickfish pictured above, is used multiple times in the new model, and element designer Mateo has explained why fins are represented with one element, rather than multiple.

"We developed one new element for the fins," detailed Mateo. "We decided not to do two specific elements, but rather do something generic that you can use to adapt to different fish. So the element looks like that, and I tried to make it simple enough so it can be different parts, and also, you can adapt it to different sizes of fish."

By stacking multiple pieces on one another, the fin element can take on different shapes and sizes, and its curve allows it to blend in perfectly with a standard LEGO slope. It's a clever use of the new element immediately, and it will be interesting to follow this piece's journey in 2026 and beyond to see just how versatile it can be with time.

LEGO Icons 10366 Tropical Aquarium goes on sale on LEGO.com and in physical stores from November 13 for LEGO Insiders or November 16 widely, retailing at £399.99 / $479.99 / €449.99. LEGO Insiders ordering before November 19 or while stocks last will receive a free 5009823 Fish Tank Filter & Fish Food.

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