Tuna

Tuna is a free-to-play item on the OSRS Grand Exchange in the other category.

In-game examine text: "Wow, this is a big fish."

It has a Grand Exchange buy limit of 6,000 every four hours, a high alchemy value of 24 gp, and item ID 361.

View on OSRS Wiki

Tuna shows an active flip setup with a margin of +11 gp and 387,040 trades over the last 24 hours.

At the buy limit of 6,000 every four hours, max profit per cycle is about 66.0k gp — high margin with healthy liquidity.