fluid-aquarium

Fluid Aquarium

tx3 protocol for FluidTokens Aquarium — babel fees and scheduled transactions on Cardano.

Status: WIP — This tx3 off-chain implementation is under testing and may not cover all edge cases yet.

Overview

Fluid Aquarium allows users to create "tanks" (UTxOs with ADA) that can be consumed by:

• Babel fee bots: Pay a user's transaction fees in exchange for native tokens at an oracle-determined rate
• Aquarium nodes: Execute scheduled transactions at a specified future time

Users can also stake FLDT tokens to register as Aquarium node operators.

Transactions

Transaction	Description
create_babel_tank	Create a tank for babel fee payments (ADA deposit + datum)
create_scheduled_tank	Create a tank for scheduled transaction execution
withdraw_tank	Reclaim ADA from an owned tank
consume_oracle	Batcher consumes part of a tank's ADA, paying the owner in tokens at oracle rate
execute_scheduled	Batcher executes a scheduled transaction after its execution time
stake_fldt	Stake FLDT tokens to become an Aquarium node operator

Important Considerations

• Tank creation is script-free: create_babel_tank and create_scheduled_tank are plain payments with inline datums — no validators execute.
• Oracle validation: consume_oracle uses a withdrawal-based oracle (0 ADA withdrawal with redeemer). The oracle redeemer currently supports Charli3 price feeds.
• Withdrawal redeemer: Fixed (tx3#317). The reward redeemer is now correctly compiled into the witness set.
• Raw CBOR datums: Tank creation transactions use raw CBOR for the datum (tank_datum_cbor) because the TankDatum type contains nested lists and optional types that are complex to pass as parameters.
• Oracle datum not readable via datum_is: The Charli3 oracle provider datum uses a Map-based CBOR format (Constr(0, [Constr(2, [Map {...}])])) which tx3 types cannot model (they require positional constructor fields). Oracle values must still be passed as individual params.
• Reference inputs ordering: consume_oracle relies on multiple reference inputs (oracle provider, oracle contract, staker, parameters NFT, tank ref script) — their indices in the transaction must match the redeemer fields.
• Staker redeemer: stake_fldt uses a raw CBOR redeemer (staker_redeemer_cbor) due to tx3 limitations on custom types as parameters.

Caller Preparation

Several values must be prepared off-chain before invoking transactions:

create_babel_tank / create_scheduled_tank

• tank_datum_cbor: Bytes — The full tank datum must be serialized as raw CBOR by the caller. The TankDatum type contains nested lists, optional types, and on-chain Address structures too complex to pass as individual parameters.

consume_oracle

This transaction requires extensive off-chain data:

• Oracle price data: oracle_price, oracle_denominator, oracle_valid_from, oracle_valid_to, oracle_token_policy, oracle_token_name — queried from the Charli3 oracle datum on-chain.
• Reference input indices: input_tank_idx, oracle_idx, ref_params_idx, oracle_provider_idx, paying_token_idx — must match the actual ordering of inputs in the built transaction.
• Payment calculation: payment_ada, payment_token_qty, tank_return_ada, dest_ada — computed from the oracle price and tank contents.

execute_scheduled

• batcher_addr_cbor: Bytes — The batcher's on-chain Address must be CBOR-encoded externally (tx3 cannot construct Plutus Address types as params).
• signer_hash: Bytes — The batcher's staking key hash (not payment key). tx3's signers block only extracts payment keys.

stake_fldt

• staker_redeemer_cbor: Bytes — The staker redeemer must be serialized as raw CBOR due to tx3 limitations on custom types as parameters.
• signer_hash: Bytes — The user's staking key hash (same reason as above).

tx3 Limitations

Several tx3 language limitations affect this protocol. Three were resolved with unreleased fixes: field name shadowing (tx3#316), withdrawal redeemer generation (tx3#317), and typed reference datum access (tx3#318). Remaining limitations include custom types as params, list values as invoke args, and staking key extraction. For the full list, see investigacion/tx3-limitations-aquarium.md.

Smart Contracts

• PlutusV3 (Aiken v1.1.9)
• Source: FluidTokens/ft-cardano-aquarium-sc