Overview
Aquarium is a decentralized protocol on Cardano that lets you pay network fees with any token you already hold, so you don't have to keep a separate stash of ADA just to send things1. Pick what you want to send, pick the token you want to spend, and the app sorts out the rest2.
It's built by FluidTokens, a team behind a family of Cardano apps for lending, renting, and earning yield. The idea of paying fees in any token was described by Input Output, the network's original engineering company, in a 2021 article that called it Babel fees3. Aquarium brings Babel fees to Cardano2.
Key Features
- Pay the network fee with a token instead of ADA. Pick the token you want to spend, and Aquarium handles the ADA part of the fee in the background2. Stablecoins and other Cardano tokens can be used for the fee4.
- Cover other people's fees in exchange for their tokens. Put some ADA in a "fee tank" and it pays the ADA part of other users' transaction fees. In return, the tank receives their tokens at an exchange rate you choose, either fixed or calculated by FluidTokens oracles1,4.
- Schedule a payment for later. Set up a transaction to go out once at a future time or to repeat on a schedule. A group of independent operators races to carry it out at the right moment1.
- Independently audited code. Anastasia Labs, a Cardano security firm, reviewed Aquarium's smart contracts in late 2024, and the full report is public5.
- Public, inspectable code. The code that runs fee tanks and scheduled payments is public in the FluidTokens GitHub organisation, so anyone can review it1.
What to Expect
The Aquarium homepage shows three cards: pay a fee in any token, set up a fee tank, or schedule a payment. Each one starts by connecting a Cardano wallet, a self-custody app that holds your keys. The "Try Babel Fees" card is the friendliest place to start: pick what to send, pick which token covers the fee, and the form fills in the rest. The other two cards are for people who want to cover other users' fees with their own ADA or schedule payments.
For builders, the Aquarium homepage says other apps can integrate Aquarium through its APIs, and it points developers to the FluidTokens Discord to set that up2. People who run an Aquarium node can also switch on an optional bot that liquidates loans on FluidTokens' lending protocol6. The full documentation sits at docs.fluidtokens.com, where Aquarium lives next to FluidTokens' other Cardano products7.
